LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


BIOLOGY 

LIBRARY 

G 


Class 


BOOKS  BY  B.  P.  COLTON 


Physiology:  Experimental  and  Descriptive. 

For   High   Schools,  Normal   Schools,  and   Colleges.      440 
pages.     Illustrated  in  colors. 

Physiology :  Briefer  Course. 

For  High  Schools.     400  pages.     Illustrated  in  colors. 

Elementary  Physiology  and  Hygiene. 

For  grades  below  the  High  School.     320  pages.     Illustrated. 

Zoology:  Descriptive  and  Practical. 

PART    I.  —  DESCRIPTIVE.    376  pages.    Illustrated. 
PART  II.  — PRACTICAL.    234  pages. 


D.    C.    HEATH   &   CO.,   PUBLISHERS 
BOSTON  NEW  YORK  CHICAGO 


ZOOLOGY 


DESCRIPTIVE    AND    PRACTICAL 


BY 


BUEL  P.  COLTON,  A.M. 


AUTHOR   OF    "  PHYSIOLOGY,  EXPERIMENTAL  AND  DESCRIPTIVE,"  "  PHYSIOLOGY 

ILLUSTRATED    BY    EXPERIMENT,"    "  ELEMENTARY   PHYSIOLOGY," 

"PRACTICAL    ZOOLOGY";  ,  AND    PROFESSOR   OF   NATURAL 

SCIENCE   IN   THE   ILLINOIS   STATE   NORMAL 

UNIVERSITY 


I 
DESCRIPTIVE 


^'     Of   THE 

UNIVERSITY 

OF 


BOSTON,   U.S.A. 

D.   C.   HEATH   &   CO.,   PUBLISHERS 
1907 


THE  VOICE  OF  THE   SEA  LIBRARY 

"The  child  holds  a  shell  to  his  ear  and  hears  the  roaring  of 
the  sea.  Do  not  yet  tell  him  that  the  sound  he  hears  is  only 
the  echo  of  the  rushing  of  blood  in  his  own  head.  In  a  higher 
sense  the  child  is  right.  To  him  it  speaks  of  the  sea,  its  home. 
It  brings  the  inland  child  a  message  from  the  vast  ocean  —  the 
distant  —  the  mysterious.  It  widens  his  narrow  horizon;  it 
takes  him  to  the  shore  whose  waters  wash  all  other  shores.  He 
is  no  longer  isolated,  but  put  in  touch  with  all  the  world.  And 
this  typifies  the  broad  principle  that  one  fact  —  considered  in  all 
its  relations  —  involves  the  whole  universe." 


COPYRIGHT,  1903, 
BY   BUEL  P.  COLTON. 


PREFACE. 


THE  PLAN.  —  The  general  plan  of  the  book  is  to  introduce  each  of 
the  larger  groups  of  animals  by  the  careful  study  of  a  typical  repre- 
sentative. It  is  the  aim  to  present  a  fairly  complete  picture  of  the  life 
of  this  type,  —  its  place  of  living ;  its  manner  of  securing  food ;  its 
enemies  and  its  means  of  protection ;  its  mode  of  locomotion ;  the 
processes  of  digestion,  circulation,  and  respiration ;  its  sense  organs ; 
its  development ;  its  relations  to  the  plant  world,  to  other  animals,  and 
to  man.  Following  the  study  of  the  type  is  a  general  account  of 
representative  forms  The  characteristics  of  the  group  are  given  in 
summarized  form.  Each  chapter  closes  with  a  tabular  classification 
of  the  group. 

TIME  FOR  THE  STUDY  OF  ZOOLOGY.  —  Of  the  three  seasons  during 
which  school  is  in  session,  winter  is  the  least  desirable  for  the  study 
of  animals.  Many  of  the  birds  have  migrated ;  most  of  the  insects 
have  been  killed ;  those  that  remain  alive  are  in  close  hiding  and  are 
hard  to  find,  and  still  more  so  are  their  eggs,  larvae,  or  pupae.  A  large 
number  of  animals  are  hibernating.  Animal  life  is  at  low  ebb.  The 
choice  of  time,  then,  is  practically  limited  to  fall  and  spring.  While 
there  is  an  abundance  of  life  in  the  spring  and  some  forms  can  better 
be  studied  then,  on  the  whole  animal  life  is  at  its  highest  activity  in  the 
fall.  Again,  since  spring  is  preferred  for  botany,  the  fall  seems  the 
best  time  for  zoology. 

THE  ORDER  OF  STUDY.  —  The  chief  aim  is  to  understand  the  lives 
of  animals.  To  know  them  it  is  necessary  to  study  them  in  relation  to 
their  surroundings.  To  do  this  to  the  best  advantage  they  should  be 
studied  when  at  the  hight  of  their  activity.  These  points,  then,  must 
largely  determine  the  order  of  study.  For  instance,  if  zoology  is  begun 
in  the  fall,  one  finds  insects  active  and  abundant.  Many  forms  are 
laying  their  eggs  to  produce  the  generation  of  the  following  spring. 


212402 


iv  Preface. 

They  should  be  studied  before  the  season  of  frosts.  On  the  other 
hand,  fishes  can  as  well,  or  better,  be  studied  later.  Since  the  natural 
history  point  of  view  is  prominent,  the  general  principle  regulating  the 
order  of  study  should  be,  "  follow  the  season."  The  birds,  too,  should 
receive  attention  during  the  first  part  of  the  term,  for  many  of  them 
migrate  early.  It  is  not  necessary,  nor  always  desirable,  to  complete 
the  study  of  one  group  before  beginning  another.  Two  lines  of  work 
can  profitably  be  pursued  on  alternate  days  or  weeks. 

P'or  fall  work,  the  order  here  given  has  been  found  satisfactory. 
But  circumstances  call  for  considerable  variation ;  it  is  not  necessary  to 
follow  any  given  order  with  slavish  fidelity.  If  the  work  begins  in  the 
spring,  the  teacher  may  prefer  to  begin  with  the  crayfish,  clam,  fish, 
or  frog. 

There  are  some  advantages  in  beginning  with  the  lowest  animals 
and  studying  them  in  the  ascending  order.  This  gives  the  clearest 
idea  of  the  natural  sequence  of  the  animal  kingdom. 

Other  things  being  equal,  it  would  be  better  to  study  animals  in  their 
logical  sequence,  just  as  we  prefer  to  learn  historical  facts  in  their 
chronological  order.  But  there  are  very  serious  objections  to  this 
order.  First,  it  involves  the  use  of  the  microscope  at  the  outset.  This 
is  impossible  for  many  schools.  Further,  the  use  of  the  microscope  is 
like  a  new  language,  which  must  be  translated.  Even  if  the  student 
has  a  microscope  and  has  mastered  its  technique,  he  still  has  difficul- 
ties. What  he  sees  is  very  different  from  his  previous  observations. 
All  our  knowledge  is  knowledge  of  relation.  Until  the  new  is  related 
to  that  already  known,  it  means  nothing.  The  very  simplicity  of  the 
Protozoan  makes  it  hard  to  understand 

If,  however,  the  teacher  decides  upon  this  course,  the  work  may 
begin  with  Chapter  XVIII.  '  By  following  the  remaining  chapters  and 
then  beginning  with  Chapter  I,  the  ascending  order  will  be  followed 
with  a  few  slight  exceptions.  But,  as  before  stated,  the  teacher  should 
not  be  tied  down  to  any  fixed  order.  Zoology  is  the  study  of  animals. 
For  most  schools,  the  best  time  to  study  animals  is  when  they  can  be 
most  easily  collected,  for  two  reasons.  First,  it  involves  expense  to 
keep  them  on  hand  to  use  at  a  later  date.  Second,  and  more  impor- 
tant, the  sooner  they  are  studied  after  collection,  the  better.  At  this 
time  some  of  the  facts  as  to  their  source  will  appear,  even  if  the  students 
have  not  assisted  in  the  collecting.  The  study  of  the  home  life  and 
natural  surroundings  is  of  vital  importance,  if  the  student  is  to  get 


Preface.  v 

beyond  morphology  into  the  fields  of  natural  history,  ecology,  and 
economic  relations. 

THE  PLACE  OF  NATURE  STUDY.  —  Many  teachers  of  natural  his- 
tory are  accused,  often  very  justly,  of  placing  too  high  a  value  on  the 
subject.  The  true  teacher  will  try  to  see  the  real  place  of  his  subject 
in  the  course  of  study.  Natural  history  cannot  claim  the  highest  place. 
Interesting  as  are  the  actions  of  animals,  they  cannot  compare  with  the 
deeds  of  men.  History  is  above  natural  history  as  man  is  above  the 
other  animals.  But  the  student  who  has  formed  the  habit  of  seeking 
the  meanings  of  facts  in  natural  history  will  carry  this  habit  into  the 
study  of  history.  The  study  of  natural  history  should  come  first,  for 
children  are  interested  in  animals.  The  habits  of  observation  and 
interpretation  once  formed  will  be  carried  through  life  and  applied  in 
every  line  of  thought.  To  cultivate  these  habits  should  be  the  con- 
stant aim  of  the  teacher.  The  study  of  animals  especially  lends  itself 
to  such  training,  because  of  the  child's  inherent  interest  in  the  subject, 
and  because  of  the  varied  adaptations  to  ^eir  surroundings  that  animals 
everywhere  exhibit. 

THE  INTERPRETATION  OF  NATURE.  —  The  study  of  the  relations 
of  animals  to  their  surroundings  is  a  constant  investigation  of  cause. 
The  student  must  ask  why  an  animal  has  a  certain  color,  form,  or  habit. 
He  must  first  learn  to  observe  the  facts  that  come  within  the  range 
of  his  experience.  Next,  he  must  seek  an  explanation  of  these  facts. 
He  must  become  possessed  by  the  idea  that  every  fact  has  a  meaning, 
and  that  it"  is  worth  while  to  think  out  this  meaning.  At  first  he  must 
be  helped ;  but  he  is  to  learn  that  he  must  rely  mainly  on  himself  for 
the  solution  of  the  problems  of  animal  life. 

CLASSIFICATION.  — It  is  highly  important  that  the  student  learn  how 
to  classify  animals ;  that  he  commits  to  memory  a  system  of  classifica- 
tion is  of  doubtful  value.  To  classify  is  simply  to  sort,  or  to  arrange, 
things  according  to  their  likenesses.  The  child  sorts  his  blocks;  that 
is,  he  puts  those  of  a  kind  together.  Those  of  different  kinds  are 
separated.  This  is  classification,  —  a  grouping  according  to  resem- 
blances and  differences.  But  the  child  cannot  sort  blocks  unless  he 
has  them.  Neither  can  the  student  classify  animals  unless  he  knows 
them.  It  is  impossible  to  classify  the  unknown. 


vi  Preface. 

As  the  facts  concerning  the  different  kinds  of  animals  become  known, 
they  must  be  sorted  and  arranged  according  to  some  system.  The 
basis  of  classifying  animals  is  structure.  Of  course  the  beginner 
cannot  go  deep  into  anatomy,  but  he  must  know  some  of  the  more 
important  facts  of  structure  or  else  his  attempt  at  classification  is  com- 
paratively useless.  Since  it  is  usually  impracticable  to  study  animals 
in  systematic  order,  the  student  must  learn  to  arrange  his  knowledge 
as  he  proceeds.  This  is  not  different  from  mental  growth  in  other 
lines.  Our  experiences  do  not  come  to  us  classified.  Just  as  an 
orderly  merchant  sorts  his  new  goods,  and  arranges  them  on  shelves 
with  previously  acquired  articles  of  the  same  kinds,  so  the  student  must 
arrange  in  systematic  order  his  ever  increasing  stock  of  knowledge. 

At  the  close  of  the  volume  will  be  found  the  classification  of  the 
animal  kingdom  according  to  Parker  and  Haswell,  whose  arrangement 
is  considered  the  most  authoritative  of  recent  works. 

THE  VALUE  OF  THE  STUDY  OF  TYPES.  —  Real  knowledge  comes 
through  experience.  What  one  learns  through  another  is  information. 
The  teacher  must  distinguish  between  first-hand  knowledge  and  second- 
hand knowledge.  Now  the  number  of  animals  that  any  student  can 
examine  is  small  in  comparison  with  the  number  in  existence.  The 
study  of  the  animal  kingdom  is  greatly  simplified  by  the  fact  that,  with 
all  the  variety  of  animal  forms,  there  are  actually  but  few  different  plans 
of  structure.  One  important  part  of  the  teacher's  work  is  to  select  the 
best  types  for  careful  study.  On  the.  foundation  thus  laid  much  infor- 
mation may  be  built.  If  one  had  never  seen  a  Crustacean,  he  would 
get  little  from  reading  about  Crustaceans.  But,  after  studying  a  cray- 
fish, a  fairly  clear  idea  of  a  lobster  or  a  crab  may  be  obtained  by  read- 
ing, for  a  foundation  has  been  laid  in  sense  perception. 

The  knowledge  of  a  type  may  ba  compared  to  a  peg  in  a  wall ;  if  it 
is  driven  in  solid,  it  will  hold  many  facts  of  information. 

The  types  selected,  their  number,  and  the  thoroughness  with  which 
they  are  studied  will  naturally  vary  with  the  locality,  season,  the  age 
of  the  student,  the  time  allotted  to  the  study,  and  various  other 
circumstances. 

DEFINITIONS.  —  The  student  should  be  taught  to  make  definitions. 
By  comparing  a  number  of  related  forms,  as  suggested  in  the  practical 
work  on  insects,  the  student  should  see  what  characteristics  they  have 


Preface.  vii 

in  common.  Thus  he  is  enabled  to  distinguish  groups.  Memorized 
definitions  have  comparatively  little  value.  "A  neat  definition  is  a 
very  attractive  thing.  It  seems  to  offer  the  sum  and  substance  of 
wisdom  in  portable  form.  But  to  understand  it,  to  comprehend  what 
it  includes  and  what  it  excludes,  the  thoughts  of  the  master  must  be 
gone  over  again  in  the  mind  of  the  disciple,  —  and  then  he  no  longer 
needs  the  definition."  But  definitions,  however  made,  are  often  mis- 
leading. The  fact  is  that  nature  has  not  sharply  and  distinctly  sepa- 
rated animals  into  groups.  There  are  usually  no  -hard  and  fast  lines 
between  them.  If  we  try  to  establish  a  dividing  line,  we  almost  always 
fi:^  ;t  cutting  across  some  intermediate  forms.  Since  the  groups  of 
animals  overlap,  and  gradually  shade  off  one  into  another,  it  is  better 
not  to  try  to  think  of  them  as  having  definite  boundary  lines.  We 
should  rather  consider  each  group  as  arranged  about  a  type  at  the 
center. 

PRACTICAL  WORK.  —  It  has  been  thought  best  to  place  the  practical 
work  in  the  latter  part  of  the  book.  But  this  work  should,  of  course, 
precede  the  assignment  of  lessons  in  the  descriptive  text.  Effort  has 
been  made  to  correlate  the  two  parts  so  that  they  may  be  used  together 
to  good  advantage.  The  author  is  well  aware  that  in  many  schools  the 
facilities  for  field  and  laboratory  work  are  very  limited.  He  has,  there- 
fore, thought  best  to  err  on  the  safe  side  and  give  rather  full  descrip- 
tions. But  the  teacher  should  see  to  it  that  the  student  himself  solves 
as  many  as  possible  of  the  problems. 

The  teacher  may  find  help  in  the  "  Suggestions  to  the  Teacher  of 
Zoology,"  which  is  issued  in  pamphlet  form  by  the  publishers  of  this 
book. 

ECONOMIC  IMPORTANCE  OF  ANIMALS.  —  The  common  schools  aim 
primarily  at  intellectual  acquisition  and  training  rather  than  at  indus- 
trial application.  Still,  the  economic  side  of  the  study  of  animals 
should  be  kept  clearly  in  mind.  The  public  has  a  right  to  demand 
that  the  knowledge  gained  in  school  shall  have  some  practical  value. 
The  economic  side,  too,  is  one  of  the  most  interesting,  and  should 
receive  attention  for  this  reason,  if  for  no  other.  This  is  a  line  of  work 
in  which  collateral  reading  may  be  most  profitably  followed.  There 
are  many  Reports  of  the  Department  of  Agriculture  which  may  be 
obtained  free  on  application  to  the  Department  of  Agriculture,  Wash- 


viii  Preface. 

ington,  D.C.  These  pamphlets  may  serve  as  the  nucleus  of  a  reference 
library.  These  reports,  and  as  many  other  books  as  the  school  can 
afford,  should  be  accessible  to  the  student,  and  he  should  be  encouraged 
to  use  them  freely. 

ACKNOWLEDGMENT.  —  The  manuscript,  entire  or  in  part,  has  been 
critically  read  by  Professors  M.  A.  Bigelow,  Teachers  College,  Columbia 
University;  H.  Carman,  State  College  of  Kentucky;  F.  R.  Lillie, 
University  of  Chicago  ;  T.  H.  Montgomery,  University  of  Pennsyl- 
vania; M.  M.  Ricker,  Burlington,  Iowa;  and  J.  M.  Tyler,  Amherst 
College.  The  manuscript  has  been  corrected  by  Miss  Chestine  Gowdy, 
teacher  of  grammar,  Illinois  State  Normal  University. 

The  proofs  have  been  read  by  Professors  M.  F.  Arey,  State  Normal 
School,  Cedar  Falls,  Iowa ;  A.  C.  Boyden,  State  Normal  School,  Bridge- 
water,  Massachusetts;  M.  J.  Elrod,  University  of  Montana;  J.  W. 
Folsom,  University  of  Illinois  ;  H.  Carman,  State  College  of  Kentucky ; 
W.  S.  Jackman,  University  of  Chicago ;  H.  S.  Jennings,  University  of 
Michigan ;  J.  M.  Johnson,  Peter  Cooper  High  School,  New  York ; 
S.  J.  Hunter,  University  of  Kansas;  Louis  Murbach,  Detroit  High 
School;  Frank  Smith,  University  of  Illinois;  H.  B.  Ward,  University 
of  Nebraska.  To  all  of  these  the  author  extends  his  most  sincere 
thanks.  Their  criticisms  have  weeded  out  many  errors ;  but  for  those 
that  remain  they  are  in  no  way  responsible. 

In  most  cases  the  sources  of  the  cuts  are  indicated  in  the  captions. 
About  forty  of  the  cuts"  are  original.  The  drawings  of  the  clam  were 
made  by  Mr.  Frank  J.  George,  now  a  teacher  in  the  Philippines.  Most 
of  the  other  original  drawings  were  made  by  Miss  Esther  Mohr. 

NORMAL,  ILLINOIS, 
February  19,  1903. 


CONTENTS. 

CHAPTER  PAGE 

I.     BRANCH  ARTHROPODA  —  Class  Insecta i 

II.     BRANCH  ARTHROPODA  —  Class  Insecta  {Continued)        .         .  25 

III.  BRANCH  ARTHROPODA 54 

Class  i.    Myriapoda 54 

Class  2.    Arachnida 55 

IV.  BRANCH  ARTHROPODA  —  Class  Crustacea  61 
V.     BRANCH  ARTHROPODA  —  Class  Crustacea  (Continued)    .         .  77 

VI.     BRANCH  ANNULATA  —  The  Segmented  Worms         ...  87 

VII.     BRANCH  MOLLUSCA  —  Class  Pelecypoda 102 

VIII.     BRANCH  MOLLUSCA  —  Class  Gastropoda 127 

IX.     BRANCH  MOLLUSCA  —  Class  Cephalopoda        ...  138 

X.    BRANCH  CHORDATA 148 

Subbranch  Urochorda        . 148 

Subbranch  Vertebrata 151 

Class  i.   Cyclostomata .  153 

Class  2.    Pisces 154 

XI.     BRANCH  CHORDATA  —  Class  Pisces  (Continued)     .        .        .168 

XII.     BRANCH  CHORDATA  —  Class  Amphibia 181 

XIII.  BRANCH  CHORDATA  —  Class  Reptilia 196 

XIV.  BRANCH  CHORDATA  —  Class  Aves 208 

XV.     BRANCH  CHORDATA  —  Classification  of  Aves    .        ...        .  222 

XVI.     BRANCH  CHORDATA  —  Class  Mammalia 246 

XVII.     BRANCH  CHORDATA  —  Classification  of  Mammalia   .        .         .  256 

XVIII.     BRANCH  PROTOZOA  —  The  One-celled  Animals        .        .        .  286 

XIX.     BRANCH  PORIFERA  —  The  Sponges  .        .....  307 

XX.    BRANCH  CCELENTERATA 313 

Class  i.   Hydrozoa 317 

Class  2.   Scyphozoa 323 

Class  3.   Actinozoa .  325 


Contents. 


CHAPTER  PAGE 

XXI.    BRANCH  ECHINODERMATA       .        .        .        .        .        .        .331 

Class  i.   Asteroidea  . 331 

Class  2.    Ophiuroidea         .......  337 

Class  3.    Echinoidea  . 338 

Class  4.    Holothuroidea 343 

Class  5.   Crinoidea 345 

XXII.    BRANCH  PLATYHELMINTHES — The  Flatworms        .        .        .  348 

BRANCH  NEMATHELMINTHES — The  Roundworms  .        .        .  351 

BRANCH  TROCHELMINTHES  —  The  Rotifers      .        .        .        .  352 

BRANCH  MOLLUSCOIDA .        .  353 

XXIII.    CLASSIFICATION  OF  THE  ANIMAL  KINGDOM   ....  355 

INDEX    .       „ .       -359 


ZOOLOGY:    DESCRIPTIVE    AND 
PRACTICAL. 


PART    I.     DESCRIPTIVE. 

CHAPTER    I. 
BRANCH   ARTHROPODA. 

CLASS   INSECTA. 
Example.  —  The  Grasshopper. 

The  Life  of  an  Animal.  —  In  order  to  understand  the  life 
of  any  animal,  try  to  get  answers  to  such  questions  as  these  : 
Where  does  it  live?  How  is  it  adapted  to  its  surround- 
ings? What  does  it  "eat,  and  how  does  it  get  its  food? 
What  are  its  enemies,  and  how  does  it  escape  them  ? 
What  is  its  chief  mode  of  locomotion  ?  What  is  it  doing 
most  of  the  time  ?  What  seems  to  be  its  main  object  in 
life  ?  What  changes  does  it  undergo  in  its  growth  ?  Does 
it  eat  the  same  kind  of  food,  breathe  in  the  same  way, 
move  in  the  same  way,  or  live  in  the  same  conditions  dur- 
ing the  different  stages  of  its  development  ?  How  does  it 
affect  plant  life  ?  What  is  its  influence  on  other  animals  ? 
Is  it  useful,  either  directly  or  indirectly,  to  man  ?  Is  it 
either  directly  or  indirectly  injurious  to  man  ? 

Home  Life  of  a  Grasshopper.  —  As  indicated  in  its  name, 
we  find  this  insect  on  plants.  So  well  does  its  color  har- 

i 


Insecta.  3 

monize  with  its  surroundings  that  we  often  fail  to  see  the 
grasshopper  when  it  is  right  before  our  eyes.  Even  when 
we -have  frightened  a  grasshopper,  and  watch  its  jump  or 
flight,  on  going  to  the  place  where  we  saw  it  alight  we  do 
not  always  readily  discover  it. 

The  plant  on  which  the  grasshopper  rests  serves  both 
as  food  and  as  shelter ;  it  is  its  home,  so  far  as  it  can  be 
said  to  have  a  home.  Food  usually  being  abundant,  the 
grasshopper  moves  about  but  little,  and  leads  a  rather 
sluggish  life. 

Locomotion  of  the  Grasshopper.  —  The  grasshopper  has 
three  modes  of  locomotion,  crawling,  jumping,  and  flying. 
The  wings  and  legs  are  moved  by  the  strong,  white, 
striated  muscles,  which  are  situated  chiefly  in  the  thorax. 

Crawling.  —  This  is  accomplished  mainly  by  the  first  and 
second  pairs  of  legs,  the  hind  pair  making  fewer  movements 
in  the  ordinary  slow  crawl.  The  hooked  claws  enable  the 
grasshopper  to  retain  a  firm  hold  while  crawling. 

Jumping.  —  The  length  and  strength  of  the  hind  legs  fit 
the  grasshopper  for  powerful  jumping.  The  spines  on  the 
hind  border  of  the  tibia  keep  it  from  slipping. 

The  Wings  and  Flying.  —  The  anterior  pair  of  wings 
serve  mainly  as  covers  for  the  hinder  pair,  and  their  com- 
parative thickness  and  toughness  fit  them  well  for  this  use. 
The  hinder  pair  of  wings  are  much  wider,  being  folded 
like  a  fan  when  not  in  use  and  wholly  covered  and  pro- 
tected by  the  anterior  pair.  The  hinder  pair  are  more 
delicate  in  their  texture,  but  still  are  sufficiently  strong  for 
their  work  in  flight,  being  stiffened  by  the  hollow  veins 
which  radiate  through  them.  The  grasshopper  is  crawling 
through  the  grass  or  resting  quietly  on  stems  and  leaves 
most  of  the  time,  and  is  flying  only  a  small  part  of  the 


FIG.  2.    EXTERNAL  FEATURES  OF  A  GRASSHOPPER,  DORSAL  VIEW. 

From  Packard's  Zoology. 


Insecta.  5 

time.  So  we  can  see  the  fitness  of  having  the  flying  wings 
folded  compactly  and  placed  close  to  the  sides  and  guarded. 
The  wings  are  kept  from  mutilation,  and  the  whole  insect 
is  much  less  conspicuous  than  he  would  be  with  the  wings 
outspread.  Some  grasshoppers  fly  high  in  the  air  and 
travel  long  distances. 

Respiration  in  the  Grasshopper.  —  The  spiracles  are 
shown  in  Fig.  I ;  two  pairs  of  thoracic  and  eight  pairs 
of  abdominal  openings.  From  these  spiracles,  tubes, 


FIG.  3.     CROSS  SECTION  OF  INSECT. 

a  =  Digestive  Tube. 

called  tracheae,  run  inward  to  a  trachea  extending  length- 
wise on  each  side  of  the  body.  There  is  also  a  pair  of 
dorsal  and  a  pair  of  ventral  air  tubes.  There  are,  then, 
six  air  tubes  running  lengthwise,  in  communication  with 
the  outside  air  through  the  spiracles,  and  connected  with 
each  other  by  branches.  From  these  main  tubes  branches 
extend  which  subdivide,  finely  permeating  every  part  of 
the  body,  even,  to  a  limited  extent,  the  legs  and  the  larger 
veins  of  the  wings  (see  Figs.  3  and  4).  In  addition  to  the 
air  tubes  there  are  two  rows  of  air  sacs,  which  add  to  the 


6  Descriptive  Zoology. 

buoyancy  during  flight.  The  work  of  respiration  depends 
on  the  abdomen,  as  the  thorax  is  rigid.  The  abdomen  is 
made  smaller  by  the  action  of  its  muscles,  and  expands 
again  when  they  relax.  Expiration  seems  to  be  accom- 
plished by  active  effort,  and  inspiration  by  elastic  reaction, 
just  the  reverse  of  the  breathing* process  in  man. 

Circulation  in  the  Grasshopper.  —  The  circulatory  system 
of  the  grasshopper  is  not  highly  developed.  The  only  dis- 
tinct organ  is  the  heart  (see  Figs.  3  and  4),  extending  along 


Dorsal  air-tube 


Air  sac 


FIG.  4.     AIR  TUBES  AND  AIR  SACS  OF  GRASSHOPPER. 

From  Hyatt's  Insecta. 

the  dorsal  part  of  the  abdomen.  It  is  in  the  form  of  a 
tube,  closed  behind  and  open  at  the  anterior  end.  It  has 
several  compartments,  with  valves,  which  allow  the  blood 
to  pass  forward  only.  There  are  also  openings  with  valves 
at  the  sides,  so  that  blood  enters  when  the  tube  widens,  and 
when  it  contracts  the  blood  is  pumped  forward.  The 
blood  is  colorless,  or  slightly  yellowish  or  greenish,  and 
fills  all  the  otherwise  unoccupied  spaces  of  the  body,  thus 
bathing  all  the  tissues.  The  low  development  of  the  cir- 
culatory system  is  compensated  for  by  the  high  develop- 


Insecta.  7 

ment  of  the  respiratory  system,  which  conveys  air  to  all 
parts  constantly.  Thus  the  insect  is  enabled  to  exert  its 
muscles  powerfully  and  rapidly,  and  in  general  maintain 
the  high  degree  of  activity  which  is  so  characteristic  of 
the  group.  As  might  be  expected,  the  temperature  of 
insects  is  high,  compared  with  that  of  invertebrates  in 
general,  being  several  degrees  above  that  of  the  surround- 
ing air. 

The  Grasshopper's  Food  and  Digestion.  —  Eating  is  a  large 
factor  in  the  life  of  the  grasshopper.  We  see  it  on  many 
kinds  of  plants,  gnawing  leaves  and  stems  with  its  short, 
strong,  laterally  moving  jaws.  The  narrow  gullet  extends 
upward  to  about  the  center  of  the  head,  then  turns  pos- 
teriorly and  dilates  into  the  crop,  which  runs  lengthwise 
in  the  thorax.  At  about  the  beginning  of  the  abdomen 
the  crop  narrows  somewhat  and  becomes  the  stomach. 
Alongside  the  crop  are  the  branched  salivary  glands,  whose 
ducts  run  forward  to  empty  into  the  mouth.  At  the  place 
where  the  crop  joins  the  stomach  it  is  surrounded  by  a  set 
of  six  or  eight  double-cone-shaped  pouches  extending  par- 
allel to  the  digestive  tube  itself.  These  bodies  are  the 
ceca.  They  are  hollow  and  communicate  with  the  cavity 
of  the  digestive  tube  by  openings.  The  ceca  secrete  a 
liquid  that  aids  in  digestion ;  they  increase  the  surface  of 
the  digestive  tract  and  probably  are  largely  concerned  in 
the  work  of  absorption.  The  stomach  extends  about  half 
the  length  of  the  abdomen.  Its  posterior  limit  is  marked 
by  a  large  number  of  slender  tubes,  the  urinary  tubes, 
which  enter  the  digestive  tube  at  the  juncture  of  the  stom- 
ach and  intestine.  The  last  part  of  the  intestine  is  some- 
what dilated,  forming  the  rectum,  which,  in  turn,  terminates 
in  the  anal  opening  at  the  upper  part  of  the  end  of  the 
abdomen. 


8  Descriptive  Zoology. 

Absorption  in  the  Grasshopper.  —  The  absorbed  food  ma- 
terials from  the  digestive  tube  pass  directly  into  the  general 
blood  of  the  body  cavity,  there  being  no  special  set  of 
tubes  as  in  man  and  vertebrates  generally. 

The  Excretory  System  of  the  Grasshopper.  —  The  urinary 
tubes  (formerly  called  the  malpighian  tubes)  extend  into 
the  blood  of  the  body  cavity  and  extract  from  it  essen- 
tially the  same  materials  as  the  kidneys  of  the  higher 
animals  do.  As  above  stated,  these  tubes  empty  into  the 
intestine. 

The  Nervous  System  of  the  Grasshopper.  —  The  nervous 
system  of  the  grasshopper  is  essentially  like  that  of  the 
crayfish  (Fig.  49),  consisting  of  a  row  of  ganglions  con- 
nected by  a  nerve  cord  lying  along  the  floor  of  the  body 
cavity.  It  really  is  composed  of  two  rows  of  ganglions, 
each  connected  by  its  own  chainlike  cord ;  but  usually 
the  two  corresponding  ganglions  unite,  forming  what  seems 
a  single  ganglion.  In  the  grasshopper,  the  nerve  cord  is 
plainly  double  throughout  the  head  and  thorax,  while  in 
the  abdomen  the  cord  appears  single.  There  are  ten  gang- 
lions, two  belonging  to  the  head,  three  in  the  thorax,  and 
five  in  the  abdomen.  The  first  ganglion,  often  called  the 
brain,  is  above,  or  rather  in  front,  of  the  gullet.  From  this 
the  two  strands  of  the  nerve  cord  pass  to  right  and  left  of 
the  gullet  and  again  unite  in  the  second,  or  infra-esophageal 
ganglion,  forming  the  nerve  ring  ("  nerve  collar  ")  found  in 
arthropods  and  mollusks. 

The  Senses  of  the  Grasshopper.  —  It  is  very  evident  that 
the  grasshopper  can  see  and  hear,  and  it  does  not  require 
extended  experiment  to  show  that  it  has  also  the  sense  of 
touch.  The  large  compound  eyes,  composed  of  many 
facets,  give  a  wide  range  of  vision ;  but  the  sense  of  sight 


Insecta. 


is  probably  not  very  acute,  especially  at  any  considerable 
distance.  The  clear  membrane  on  the  first  segment  of  the 
abdomen  is  the  tympanum 
of  the  hearing  organ.  The 
antennae  are  the  chief  or- 
gans of  touch. 

The  Enemies  of  the  Grass- 
hopper. —  Probably  birds 
are  the  most  formidable 
enemies  of  the  grass- 
hopper. The  grasshopper 
usually  becomes  aware  of 
the  approach  of  an  enemy 
through  sight  or  hearing, 
and  ordinarily  escapes  by 
flight  or  by  jumping.  They 
sometimes  escape  by  simply 
dropping  to  the  ground. 
The  grasshopper  is  largely 
protected  by  his  resem- 
blance in  color  to  that  on 
which  he  habitually  rests, 
some  forms  being  usually 
on  plants,  while  those  that 
stay  much  of  the  time  on 
the  ground  are  more  of  the 
color  of  the  soil.  The  posi- 
tion while  on  plants,  parallel 
to  the  stem,  makes  them 
less  conspicuous  than  they 
would  be  otherwise.  Grass- 
hoppers are  often  subject  to  injury  by  parasites,  especially 
certain  red  mites  which  are  often  to  be  found  under  the 


IO  Descriptive  Zoology. 

bases  of  the  wings.  They  are  often  destroyed  in  large 
numbers  by  the  growth  of  a  parasitic  fungus  in  their 
bodies.  Every  boy  knows  that  when  the  grasshopper  is 
captured  he  ejects  from  the  mouth  a  dark  liquid  secreted 
by  the  crop.  This  is  probably  a  means  of  defense. 

Sounds  made  by  Grasshoppers.  —  Sounds  are  produced 
by  the  males  only.  Some  grasshoppers  make  the  noise 
by  rubbing  the  bases  of  the  legs  against  the  bases  of  the 
outer  wings.  Others,  while  flying,  rub  the  under  surface 
of  the  base  of  the  outer  wing  over  the  upper  surface  of 
the  base  of  the  inner  wing.  The  katydids  and  crickets 
make  the  sound,  while  at  rest,  by  rubbing  the  wings  against 
each  other. 

Colors  of  the  Grasshopper.  —  Although  the  grasshopper 
is  decidedly  inconspicuous  when  at  rest,  on  account  of 
the  protective  resemblance  in  color,  yet  it  is  to  be  ob- 
served that  in  some  species  the  inner  wings  are  con- 
spicuously colored,  making  the  insect  very  noticeable 
during  flight. 

Development  of  the  Grasshopper.  —  The  ovaries  occupy 
the  upper  part  of  the  abdomen  of  the  female.  When  full 
of  ripe  eggs  they  take  a  good  share  of  the  space  in  the 
abdomen.  The  oviducts  extend  down  and  back,  opening 
between  the  sharp  points  at  the  end  of  the  abdomen.  These 
four  sharp  points  together  form  the  ovipositor.  In  lay- 
ing the  eggs  the  female  presses  the  tips  of  the  four 
points  close  together,  which  makes  a  strong  and  fairly 
good  digging  tool.  This  is  thrust  into  the  ground  and 
the  points  are  then  separated,  and  by  repeating  this  a  hole 
is  made,  into  which  the  eggs  are  introduced,  passing  out 
between  the  guides.  The  egg  hatches  out  into  a  little 
grasshopper  resembling  the  parent,  but  lacking  wings. 


Insecta. 


ii 


After  a  time  rudimentary  wings  appear.  In  all  such  cases 
as  this,  where  the  young  are  hatched  in  essentially  the  same 
form  as  the  adult,  the  development  is  said  to  be  direct. 

Injury  done  by  Grasshoppers.  —  Ancient  history  records 
plagues  of  locusts.  (The  name  "locust"  is  the  proper  one 
for  our  common  grasshopper.)  And  in  modern  times  and 
near-by  places  there  have  been  migrations  of  locusts  in 
such  numbers  that  they  have  darkened  the  sky,  and,  light- 
ing everywhere,  have  devastated  the  land  by  eating  almost 


FIG.  6.    GRASSHOPPER  LAYING  EGGS. 

From  Hyatt's  Insecta 

every  leaf  and  tender  stalk  of  grass,  crops,  and  trees  in 
garden  and  field.  The  Rocky  Mountain  locust,  migrat- 
ing eastward,  almost  produced  a  famine  in  Kansas  and 
Nebraska,  and  created  terror  beyond  the  limits  of  its  actual 
ravages.  But,  fortunately,  the  young  hatched  in  the  lower 
states  are  not  healthy,  and  die  prematurely ;  hence  the 
plague  has  not  spread  so  extensively  as  it  threatened  to  do. 
Packard  says  that  the  Rocky  Mountain  locust,  within  a 
period  of  four  years,  inflicted  a  loss  of  $200,000,000  on  the 
farmers  of  the  West. 


12  Descriptive  Zoology. 

ORDER   ORTHOPTERA. 

The  Orthoptera.  —  We  have  selected  the  grasshopper  as 
'the  best  available  type  of  the  class  Insecta  and  also  of  the 

order  Orthoptera.  The  word 
Orthoptera  means  straight - 
winged,  probably  in  allusion  to 
the  mode  of  folding  the  hind 
wings.  The  first  pair  are  thick- 
ened, serving  as  a  cover  for  the 
second  pair,  which  are  folded 
when  at  rest.  The  mouth  parts 
are  fitted  for  biting.  The  de- 
velopment is  direct. 

Protective  Resemblance. — 

The  green  grasshoppers,  es- 
pecially the  katydid,  are  note- 
worthy for  their  resemblance  to 
leaves,  both  in  color  and  form. 
The  walking  stick  (Fig.  7)  so 
closely  resembles  a  twig  that 
it  is  seldom  discovered  by 
casual  observers.  These  in- 
sects afford  fine  examples  of 
the  advantages  of  protective 
resemblance. 

The  green  grasshoppers  have 
a  windowlike  membrane  on  the 
FIG.  7.   A  WALKING  STICK  INSECT  tibia  of    each   fore    leg  that  is 

(Diapheromerafemorafa)  ON  TWIG.    supposed     to     be    an    organ      of 
From  Jordan  and  Kellogg' s  Animal  Life.  , 

hearing. 

Classification  of  Orthoptera. — The  families  are :  the  short- 
horned   grasshoppers  (locusts),   which  we  have   studied ; 


Insecta.  13 

the  long-horned  grasshoppers  (usually  green),  including 
the  katydid ;  the  crickets  ;  the  cockroaches,  including  the 
"croton  bug,"  so  common  about  water  pipes;  the  walking 
sticks ;  and  the  mantids. 


ORDER   ODONATA. 

The  Dragon  Fly.  —  The  dragon  fly  has  a  long,  straight 
abdomen,  and  large  eyes.  The  two  pairs  of  net-veined 
wings  are  alike  in  texture  and  nearly  of  the  same  size. 
The  wings  are  never  folded,  but  when  at  rest  are  held  out 
at  right  angles  to  the  body,  ready  for  instant  use.  There 
is  a  pair  of  strong  jaws,  which  are  nearly  covered  by  the 
large  under  and  upper  lips.  The  dragon  fly  feeds  on  in- 
sects, which  it  catches  on  the  wing,  being  one  of  the 
swiftest  and  strongest  flying  of  insects.  Dragon  flies  are 
most  abundant  in  marshy  places,  where  they  may  be  seen 
flying  over  the  water  or  perched  on  a  leaf  or  stem  above 
the  water,  on  the  alert  for  a  passing  mosquito  or  other 
small  insect.  The  females  lay  the  eggs  in  the  water,  and 
may  often  be  seen  hovering  over  the  water  with  the  tip  of 
the  abdomen  dipping  beneath  the  surface.  .  An  egg  hatches 
into  a  form  called  a  nymph,  with  strong  jaws.  It  immedi- 
ately begins  to  prey  upon  other  insects  and  larvae  that  it 
finds.  When  it  has  attained  its  growth  it  crawls  up  the 
stalk  of  some  water  plant,  splits  along  the  back,  and  the 
dragon  fly  emerges,  leaving  the  empty  skin  still  clinging 
to  the  stalk.  The  development  is  here  also  called  direct. 
While  living  in  water  the  larva  breathes  by  taking  water 
into  the  hind  part  of  the  digestive  tube.  Other  dragon  fly 
larvae  have  rudimentary  gills.  Some  of  the  smaller  dragon 
flies,  when  at  rest,  place  the  wings  close  together,  just  above 
the  body.  These  are  called  damsel  flies.  Dragon  flies  are 


14  Descriptive  Zoology. 

also  called  darning  needles,  devil's  needles,  snake  feeders, 
snake   doctors,    spindles,   and  mosquito   hawks.      In   the 


FIG.  8.    DRAGON  FLY  AND  MAY  FLY. 

From  Hyatt's  Insecta. 

Northern  states  children  and  ignorant  adults  believe  that 
these  insects  sew  up  people's  ears,  and  in  the  South  the 


Insecta.  15 

same  classes  think  they  bring  dead  snakes  to  life.  It  is 
easy  to  see  how  these  stories  arise.  The  long  abdomen  is 
supposed  to  hold  a  correspondingly  long  sting ;  while  its 
mode  of  laying  eggs  (people  not  knowing  what  it  is  doing) 
gives  it  the  name  applied  in  the  South.  The  name  mos- 
quito hawk  is  the  most  significant  of  its  life  and  habits,  for 
it  has  no  sting,  and  is  entirely  harmless ;  but,  on  the  other 
hand,  it  benefits  man  by  destroying  mosquitos  and  other 
insects. 

Characteristics  of  Odonata. — The  dragon  flies  represent 
the  order  Odonata.  The  chief  characteristics  of  the  order 
are  :  wings  net-veined,  the  two  pairs  equal  or  nearly  so ; 
mouth  parts  fitted  for  biting ;  abdomen  long  and  slender ; 
development  direct. 


COMPARISON   OF  GRASSHOPPER  AND   DRAGON   FLY. 

GRASSHOPPER.  DRAGON    FLY. 

On  land Home Over  water 

Plants Food. Insects 

Numerous Enemies Few 

Strong  —  for  jumping Legs      .   .  Weak,  merely  for  perching 

Two  pairs Wings,  number  . Two  pairs 

First  pair  thick Wings,  texture  of   ....    Both  pairs  gauzy. 

Fold  close  to  body     .  1     Wings,  position,     j  Extended  at  right  angle 
First  pair  covering  2d  f  resting  (.....     Not  overlapping 

Crawl  through  grass  .}    .  f .  .   .   .  Dart  after  insects 

r  Position  enables  to  \  „ 
Elude  observation  .  .  J  I  Exposure  less  dangerous 

•Adaptation  to  Mode  of  Life. — In  addition  to  the  above 
tabular  representation  of  some  of  the  most  striking  differ- 
ences between  the  grasshopper  and  dragon  fly,  let  us 
consider  what  characteristics  each  has  that  fit  it  for  its 
particular  mode  and  place  of  life,  and  which  unfit  it  for 


16  Descriptive  Zoology. 

the  mode  of  life  of  the  other.  Let  us  suppose  that  they 
trade  places.  It  is  not  unfair  to  make  this  supposition,  for 
they  are  not  extremely  unlike.  Both  have  strong  biting 
jaws,  two  pairs  of  strong  wings,  and  a  long  abdomen. 

In  the  first  place,  let  us  suppose  that  the  dragon  fly  can 
subsist  on  vegetable  food,  and  that  it  takes  up  its  life  as 
a  grasshopper.  It  finds  its  long,  projecting  wings  in  the 
way.  They  not  only  hinder  it  as  it  attempts  to  crawl 
into  narrow  places,  but  are  apt  to  be  torn,  for,  though 
strong,  their  texture  is  delicate.  So  it  will  naturally  turn 
the  wings  back  alongside  of  the  body,  and  for  compact- 
ness will  probably  let  one  pair  rest  upon  the  other.  It 
will  further  protect  them  if  the  outer  wings  become  harder 
and  tougher,  but  this  change  will  be  something  of  a 
sacrifice  in  flying  power. 

Again,  when  the  wings  are  thus  folded,  the  insect  covers 
less  area  and  is  less  conspicuous  and  therefore  more  likely 
to  elude  the  eyes  of  birds  o.f  other  enemies.  Its  legs,  which 
are  light  and  weak,  having  been  used  merely  for  support, 
need  greater  strength  to  enable  it  to  crawl  and  jump.  The 
eyes  are  not  required  to  be  so  keen  and  naturally  may 
become  smaller,  and  as  it  leads  a  lazier  life  it  becomes 
more  corpulent  and^  clumsy.  To  make  up  for  the  loss  of 
flying  power  in  the  front  wings,  the  hinder  ones  become 
wider ;  this  necessitates  their  being  folded  when  at  rest 
in  order  that  the  narrower  front  wings  may  completely 
cover  them. 

Let  us  now  consider  how  the  grasshopper  would  fare 
in  the  endeavor  to  lead  the  life  of  the  dragon  fly.  In  the 
first  place,  the  grasshopper  lacks  the  flying  power  requisite 
to  capture  lively  little  insects  on  the  wing  It  must  have 
both  pairs  of  wings  developed  for  active  use ;  and  it  can 
afford  to  do  this,  as  it  does  not  need  to  have  the  front  pair 


Insecta.  17 

thickened,  as  in  its  situation  covers  are  not  needed.  It 
should  have  wings  constantly  poised,  ready  to  dart  in- 
stantly after  its  prey.  There  is  no  objection  to  having  the 
wings  continually  spread,  as  it  lives  in  open  spaces  and 
does  not  have  to  crawl  through  grass  and  twigs ;  and  the 
increased  area  due  to  the  spread  does  not  especially  endan- 
ger it  by  making  it  more  conspicuous,  since  it  has  compara- 
tively few  enemies.  The  body  is  too  heavy,  and  it  must 
"  train  down  "  until  it  can  handle  itself  better.  The  legs 
are  too  heavy,  especially  the  hind  pair ;  and,  as  it  uses  them 
very  little  except  to  perch  upon  a  leaf  or  twig,  waiting  for 
something  to  turn  up,  this  matter  takes  care  of  itself,  for 
any  unused  organ  is  likely  to  dwindle  away. 

It  needs  keener  eyes,  for  it  no  longer  feeds  on  plants 
which  are  sure  to  stay  in  place  while  it  crawls  upon  them ; 
it  is  another  matter  to  discern  small  insects  at  some  d.*- 
tance.  So  it  develops  better  eye  power  to  discover  its  food, 
as  well  as  better  wing  power  to  overtake  it  after  seeing  it. 
It  had  fairly  good  jaws  before,  but  they  become  some- 
what enlarged  and  better  adapted  to  the  new  work.  The 
enlargement  of  the  jaws  and  the  eyes  make  the  whole 
head  bigger  than  it  was  before. 

Of  course  insects  do  not  trade  places  in  this  manner; 
nor  does  any  insect  suddenly  change  its  habits.  But  we 
can  easily  imagine  that  these  two  forms  have  descended 
from  the  same  ancestors  and  have  gradually  grown  dif- 
erent,  each  becoming  fitted  for  the  situation  in  which  it  is 
placed. 

It  is  no  longer  supposed  that  all  the  forms  of  life  we 
now  see  on  the  earth  have  been  distinct  from  the  begin- 
ning, for  we  see  evidences  that  many  forms  have  arisen 
by  the  increase  in  numbers  which  establishes  competition, 
and  which  in  turn  has  compelled  dispersion  and  forced 


1 8  Descriptive  Zoology. 

adaptation  to  new  surroundings  and  a  gradual  advance- 
ment to  changed  conditions  of  life. 


ORDER   HEMIPTERA. 

The  Giant  Water  Bug.  —  This  is  the  largest  of  the  bugs, 
being  two  and  one  half  inches  long.  It  lives  in  the  water 
of  our  lakes  and  rivers,  but  was  not  very  generally  known 
until  electric  lights  became  common.  The  light  attracts 
them,  and  they  are  frequently  found  where  they  have  fallen 
under  the  lamps.  Consequently  many  people  call  them 


FIG.  9.    GIANT  WATER  BUG. 

From  Hyatt's  Insecta. 

the  "Electric  Light  Bugs."  They  are  more- abundant  in 
river  towns  that  are  lighted  by  electricity,  and  a  good  way  to 
collect  them  is  to  look  for  them  under  the  lamps  late  in  the 
evening.  By  preserving  them  in  alcohol  enough  may  be  ac- 
cumulated to  supply  a  class.  They  serve  admirably  to  show 
the  chief  characteristics  of  bugs,  and  are  large  enough  to  dis- 
sect if  the  student  wishes  to  learn  the  internal  structure. 

The  head  is  relatively  small  and  the  neck  is  not  con- 
spicuous. The  prothorax  is  large  and  broad.  The  outer 
wings  are  narrow  in  front,  being  separated  by  a  triangular 
elevation  of  the  mesothorax,  called  the  scutellum.  Then 


Insecta.  19 

for  a  short  distance  the  two  outer  wings  meet  in  the  middle 
line ;  beyond  this  the  wings  are  wider  and  overlap  each 
other.  The  hinder  part  of  the  wings  is  much  thinner  than 
the  front  part.  The  inner  wings  are  much  thinner  and  are 
folded.  The  mouth  parts  are  united  to  form  a  strong  pierc- 
ing and  sucking  tube,  which  is  bent  back  under  the  head, 
between  the  bases  of  the  front  legs.  The  features  thus  far 
described  are  common  to  nearly  all  bugs.  But  while  the 
majority  of  bugs  live  in  the  air,  the  water  bug  lives  under 
the  water  most  of  the  time,  though  it  can,  and  sometimes 
does,  come  out  and  fly  about.  To  fit  it  for  swimming  under 
the  water  the  body  is  flat  and  boat-shaped;  the  second  and 
third  pairs  of  legs  are  flattened,  especially  the  tibia  and 
tarsus,  making  admirable  paddles.  The  front  legs  are  of 
no  use  in  swimming,  but  are  used  in  grasping.  The  water 
bug  hides  under  leaves  and  sticks  in  the  water,  and  when 
an  unwary  insect,  small  fish,  frog,  or  tadpole  comes  near, 
darts  out,  seizes  it  with  its  powerful  fore  legs,  and  kills  it  by 
piercing  it  with  its  sharp  beak.  It  then  sucks  its  blood, 
having  no  jaws  for  chewing  solid  food. 

The  entomologists  do  not  describe  any  poison  glands 
in  these  insects,  but  it  would  appear  that  they  have  a  poison- 
ous effect,  since  they  seem  to  kill  their  victims  so  quickly ; 
and  since  this  and  numerous  other  bugs,  some  aquatic  and 
some  not  aquatic,  inflict  painful  wounds  on  man.  In  fact, 
the  collector  who  is  gathering  minnows  in  a  net  is  often 
bitten  by  aquatic  bugs,  and  sometimes  the  hand  and  arm 
become  painfully  swollen  as  a  result. 

Water  bugs  may  be  seen  coming  to  the  surface,  where 
they  project  the  tip  of  the  abdomen  into  the  air.  They 
breathe  through  the  anal  pair  of  spiracles. 

In  attempting  to  spread  the  outer  wing,  one  usually  meets 
difficulty,  —  the  wing  seems  to  be  caught.  There  is  an  in- 


2O  Descriptive  Zoology. 

genious  catch,  consisting  of  a  little  projection  or  hook  on 
the  side  of  the  thorax,  that  catches  into  a  groove  in  the 
under  surface  of  the  front  edge  of  the  wing. 

There  are  two  forms  of  water  bugs  common.  Belostoma 
americanum  has  a  groove  in  the  femur  of  each  front  leg, 
into  which  the  tibia  shuts  like  a  knife  blade  into  a  handle. 
The  other  form,  Benacu s  gt  iseus,  lacks  this  groove. 

The  Squash  Bug.  —  Although  smaller  than  the  giant 
water  bug,  the  squash  bug  has  the  advantage  of  being 
more  abundant.  If  the  former  cannot  be  obtained,  the 
latter  should  be  studied.  Like  the  water  bug,  it  has  a 
small  head  with  a  sharp  beak,  bent  back  under  the  head 
and  thorax.  The  outer  wings,  too,  have  a  thickened  base, 
with  the  thin  hind  portions  of  the  hind  wings  overlapping 
each  other.  The  thinner  inner  wings  are  folded  lengthwise. 
The  legs  are  adapted  to  crawling.  The  prothorax  is  large 
and  triangular.  On  the  under  surface  of  the  thorax  are 
glands  which  secrete  an  ill-smelling  liquid.  This  is  a  rather 
common  characteristic  of  Hemiptera,  and  brings  the  "bugs  " 
into  disrepute.  This  is  a  further  reason  why  we  should  not 
use  the  term  "bug"  indiscriminately  for  the  term  "insect." 
It  is  incorrect,  and  as  unfair  as  it  would  be  to  designate  all 
mankind  by  the  name  of  one  of  the  most  disagreeable  tribes 
of  savages  that  could  be  found. 

As  is  well  known,  the  squash  bug  lives  upon  plants,  suck- 
ing their  juices  through  its  strong,  piercing  beak,  doing  con- 
siderable damage,  especially  to  plants  of  the  gourd  family. 
The  eggs  are  laid  on  the  under  surface  of  the  leaves  about 
the  first  of  July,  and  in  August  the  young  may  be  seen 
with  the  wings  in  all  stages  of  development. 

The  Cicadas.  —  These  insects  are  often  improperly  called 
"locusts."  Probably  they  are  best  known  by  the  shrill 


SQUASH  BUG 


FIG.  10.    SQUASH  BUG,  STRUCTURE  AND  DEVELOPMENT. 

at,  antenna ;  la,  labium ;  mx,  maxilla ;  oc,  simple  eye ;  su,  sucking  tube. 
From  Hyatt's  Insecta. 


22  Descriptive  Zoology. 

sound  made  by  the  males.  Under  the  abdomen  of  the 
males  are  two  circular  disks.  Under  these  is  the  appa- 
ratus by  which  the  sound  is  produced. 

Both  pairs  of  wings  are  membranous,  the  hinder  pair 
being  much  the  smaller.  The  larva  is  a  grublike  form 
which  lives  under  the  ground,  sucking  the  juices  from  the 
roots  of  trees.  When  ready  to  appear  in  the  upper  world, 
it  crawls  up  the  trunk ;  and  while  it  still  clings  to  the  bark 
its  back  splits  open,  and  the  winged  insect  emerges,  leaving 


FIG.  ii.    CICADA:  HARVEST  FLY. 

From  Hyatt's  Insect  a. 

the  empty  skin  adhering  by  the  claws.  Here  the  shed  skin 
may  remain  for  weeks,  until  washed  off  by  the  rain  or 
brushed  off  by  a  passing  animal. 

The  dogday  harvest  fly  (Fig.  1 1)  has  a  very  broad  head 
with  eyes  projecting  at  its  angles,  and  is  rather  greenish. 
His  shrill  sound  is  suggestive  of  the  dry,  hot,  August  mid- 
day. The  periodical  cicada  (the  correct  name  for  what  is 
usually  called  the  "  seventeen-year  locust")  spends  from 
thirteen  years  in  the  Southern  form  to  seventeen  in  the 
Northern  in  the  larval  state.  This  cicada  is  distinctly  nar- 
rower-headed than  the  summer  cicada,  and  is  darker  in 
color. 


J  nsecta. 


Order  Hemiptera.  —  Among  the  many  exceedingly  interesting  He- 
miptera  we  may  briefly  mention  the  chinch  bugs,  so  well  and  so  unfavor- 
ably known,  and  the  plant  lice,  which  are  so  common  on  many  plants, 
especially  on  house  plants.  Noticeable  among  the  plant  lice  is  the 


FIG.  13.    PLANT  LOUSE,  WING 

Natural  size.  LESS  LARVAL  FEMALE. 


FIG.  12.    PLANT  LOUSE,  ADULT  WINGED 
FEMALE. 

From  Hyatt's  Insecta. 


On  maple 


On  osage  orange 


FIG.  14.    MAPLE  SCALE  INSECT. 

From  Hyatt's  Insecta. 


24  Descriptive  Zoology. 

grape  phylloxera,  so  injurious  to  the  grapevine.  The  scale  bugs,  or 
bark  lice,  are  very  injurious  to  trees ;  some  of  them  are  among  the  worsty 
pests  of  the  fruit  grower,  and  tax  his  utmost  ingenuity  to  prevent  their 
spreading.  The  females  are  scalelike,  and  sometimes  to  be  seen  project- 
ing from  beneath  the  scale  is  the  cottony  egg  cluster  so  frequently 
observed  on  maples. 

Two  kinds  of  bugs  are  worthy  of  mention  as  useful  to  man,  the 
cochineal  insect,  furnishing  a  dye,  and  the  lac  insect,  from  which  we  get 
shellac.  Lastly  we  refer  to  the  parasitic  Hemiptera,  such  as  the  vari- 
ous forms  of  lice,  bedbugs,  etc.  Most  of  these  forms  are  very  degen- 
erate in  their  structure,  having  lost  their  wings  as  a  result  of  their 
parasitic  habits. 

Characteristics  of  Hemiptera.  —  The  mouth  parts  form  a 
piercing  and  sucking  tube ;  the  prothorax  is  prominent ; 
fore  wings  often  thickened  at  the  base ;  many  are  ill-smell- 
ing ;  development  direct. 


ORDER   NEUROPTERA. 

The  order  Neuroptera  is  a  small  order.     The  only  ex- 
ample here  presented   is  the  ant  lion  (Figs.   15  and  16). 


FIG.  15.    ANT  LION,  ADULT.  FIG.  16.    ANT  LION,  LARVA. 

From  Hyatt's  Insecta. 


CHAPTER    II. 
BRANCH   ARTHROPODA. 

CLASS   INSECTA    (Continued}. 
ORDER  LEPIDOPTERA. 

The  Monarch,  or  Milkweed,  Butterfly.  —  This  common 
butterfly  is  of  a  brown  color,  with  black  veins  and  wing 
borders.  There  are  about  two  rows  of  white  spots  in  the 
black  border.  This  butterfly  has  a  wing  spread  of  about 
four  inches.  The  larva  is  greenish  yellow,  with  distinct 
bands  of  shiny  black,  and  feeds  on  milkweeds.  The  chrys- 
alid  is  suspended  by  the  tip,  as  shown  in  Fig.  17. 

One  of  the  most  noticeable  features  of  the  butterfly  is 
the  presence  of  scales  on  the  wings  and  body.  The  scales 
are  modified  hairs,  and  on  the  body  they  are  slender.  The 
scales  shed  water,  strengthen  the  wing,  and  serve  as  an 
ornament.  The  wings  are  large,  and  in  flying  act  together 
as  one  wing,  the  wing  motion  being  slow. 

Another  distinctive  character  is  the  long  coiled  sucking 
tube  by  which  the  butterfly  sucks  nectar  from  the  flowers. 
When  not  in  use,  this  tube  is  coiled  like  a  watch  spring 
and  concealed  between  the  labial  palps.  The  sucking  tube 
consists  of  the  two  maxillae,  much  lengthened  and  each 
grooved  along  its  inner  surface,  so  that  when  the  two  are 
closely  applied  to  each  other  they  form  a  tube.  The  man- 
dibles are  but  slightly  developed. 

In  September  or  October  great  swarms  of  these  butter- 
flies may  be  seen,  and  this  is  a  good  time  to  collect  them. 

25 


26 


Descriptive  Zoology. 


At  night  they  settle  on  trees,  hanging  in  great   clusters 
from  the  leaves.     It  is  not  easy  to  see  them  at  such  times. 


FIG.  17.    STRUCTURE  AND  DEVELOPMENT  OF  THE  MONARCH  BUTTERFLY. 

From  Hyatt's  Insecta. 

They  look  like  dead  leaves.     In  the  morning,  when  they 
are  chilled,  they  may  be  taken  in  a  net. 


Insecta.  27 

The  Cabbage  Butterfly.  —  One  of  the  easiest  of  the  butter- 
flies to  capture  and  to  rear  in  confinement  is  the  cabbage 
butterfly.  It  is  white  or  slightly  yellowish  above  and 
yellowish  below.  Both  sexes  have  black  tips  on  the  an- 


FIG.  18.  CABBAGE  BUTTERFLY,  MALE. 


FIG.  20.  CABBAGE  BUTTERFLY. 

a,  larva,  b,  pupa. 


FIG.  19.    CABBAGE  BUTTERFLY,  FEMALE. 

From  Hyatt's  Insecta 


FIG.  21.    CABBAGE  BUTTERFLY. 

Pupa. 


terior  wings ;  the  male  has  a  round  black  spot  near  the 
outer  border  of  each  wing,  while  the  female  has  two  spots 
on  each  anterior  wing.  In  the  early  fall,  watch  the  female 
laying  eggs  on  cabbage  leaves ;  gather  some  of  the  leaves 
and  watch  the  larvae  come  out  of  the  eggs ;  feed  the  larvae 
till  full  grown ;  keep  the  chrysalids  till  the  butterfly  ap- 
pears. Describe  all  the  changes  and  note  the  dates  of  all 
the  moltings  and  transformations. 


28  Descriptive  Zoology. 

The  Hawk  Moth.  —  This  moth  is  well  known  by  its  habit 
of  poising  like  a  humming  bird  over  the  flower  from  which 
it  is  extracting  the  nectar  by  means  of  its  long  sucking 
tube.  It  is  also  called  the  humming  miller,  or  humming 
bird  moth.  The  hawk  moths  have  long,  sharp-pointed 
wings  and  strong  powers  of  flight.  Their  larvae  are  usu- 
ally large  green  "  worms,"  one  of  the  most  common  being 
the  so-called  tomato  worm.  The  pupa  is  often  plowed  up 
in  gardens,  and  is  distinguished  by  the  tongue  case,  which 
is  bent  around  to  one  side  of  the  body,  like  a  pitcher 
handle.  The  hawk  moths  usually  fly  at  twilight.  The 
hawk  moths  are  also  called  sphinx  moths,  from  the  fact 
that  the  larva  often  rests  for  a  long  time  with  the  anterior 
end  held  erect. 

DIFFERENCES    BETWEEN    MOTHS  AND   BUTTERFLIES. 

BUTTERFLIES.  MOTHS. 

1 .  Day-flying,  usually.  I .  Night-flying,  usually. 

2.  Wings  erect  when  resting.  2.  Wings  sloping  when  resting. 

3.  Antennae  knobbed.  3.  Antennae  not  knobbed. 

4.  Pupa  a  chrysalid.  4.  Pupa  (often)  in  a  cocoon. 

Development  of  Lepidoptera.  — The  egg  hatches  into  what 
is  commonly  called  a  "  worm."  But  no  true  worm  has 
jointed  appendages,  while  in  these  larvae  each  of  the  first 
three  segments  back  of  the  head  bears  a  pair  of  jointed 
legs.  These  three  segments  become  the  three  segments 
of  the  thorax.  In  addition  to  these  legs  the  caterpillar,  as 
it  is  usually  called,  has  several  pairs,  commonly  five,  of 
soft,  fleshy  legs  on  segments  farther  back,  almost  always  a 
pair  on  the  last  segment.  These  prolegs  have  a  sort  of 
cleft  at  their  ends  by  means  of  which  they  aid  in  crawling. 
Some  caterpillars  are  smooth,  others  are  densely  hairy. 


FIG.  22.    HAWK  MOTH  OR  SPHINX  MOTH,  ADULT. 

From  Hyatt's  Insecta.      Larva  of  another  species. 


30  Descriptive  Zoology. 

The  larvae  eat  voraciously  and  grow  rapidly,  molting  sev- 
eral times  before  reaching  full  size.  When  ready  to  trans- 
form, the  butterfly  larva  assumes  a  harder  coat,  commonly 
ornamented  with  silvery  or  gold  markings  (hence  such  a 
pupa  is  called  a  "  chrysalid  "),  while  the  larva  of  the  moth 
may  spin  a  cocoon  of  silk,  adding  to  it  the  hairs  from  its 
body,  though  some  moths  have  a  simple,  dull-colored  pupa 
which  is  buried  in  the  ground.  The  larva  has  a  silk  gland 
which  opens  on  the  under  lip,  though  many  larvae  spin 
little  or  none,  some  making  one  or  two  loops  to  support 
themselves  when  changed  to  chrysalids,  alongside  or  under 
some  protecting  cover,  such  as  a  limb,  fence-board,  etc.  It 
should  be  noted  that  the  larvae  have  strong,  laterally  mov- 
ing jaws,  and  eat  greedily,  subsisting  on  solid  food,  whereas 
the  adult  is  a  dainty  eater,  and  lives  on  liquid  food,  which 
it  takes  through  the  sucking  tube.  It  is  common  to  speak 
of  the  Lepidoptera  as  undergoing  a  "  complete "  meta- 
morphosis, while  the  grasshopper  is  said  to  have  an  "  in- 
complete "  metamorphosis.  But  as  the  development  of  the 
locust  is  just  as  complete  as  that  of  the  butterfly,  we  should 
call  the  development  of  the  grasshopper  "  direct,"  and  that 
of  the  butterfly  "indirect." 

Kinds  of  Lepidoptera.  —  The  butterflies  are  generally  most  conspicu- 
ous, as  they  fly  in  the  daytime,  but  many  of  the  moths  are  very  beauti- 
ful. One  group  of  butterflies  are  called  from  the  form  of  their  wings 
the  swallow-tails.  Though  we  associate  the  word  "  butterfly  "  with  warm 
weather  and  sunny  days,  one  species,  the  White  Mountain  butterfly,  is 
found  only  high  in  the  mountains,  and  the  writer  has  been  delightfully 
surprised  to  find  these  beautiful  creatures  above  "timber  line,"  near 
snowbanks,  on  the  chilly  mountain  tops. 

Perhaps  most  noted  among  the  moths  is  the  silkworm,  a  native  of 
China.  But  we  have  a  number  of  native  American  silkworm  moths ; 
of  these  the  Cecropia  and  Polyphemus  are  perhaps  best  known.  The 
larva  of  the  codling  moth  is  often  found  in  apples.  There  is  a  large 


Insecta.  31 

number  of  related  moths  whose  larvae  roll  leaves,  and  are  known  as 
"leaf  rollers."  The  ''measuring  worms"  are  larvae  of  moths.  Last, 
but  not  least  in  importance,  is  the  clothes  moth,  which  departs  from  the 
usual  custom  of  living  on  vegetable  food. 

Mimicry.  —  The  viceroy  butterfly,  which  is  sometimes 
eaten  by  birds,  is  protected  by  its  resemblance  to  the  ined- 
ible monarch  butterfly.  This  is  a  case  of  mimicry. 


FIG.  25.    THE  MONARCH  BUTTERFLY. 


FIG.  26.    THE  VICEROY  BUTTERFLY,  WHICH  MIMICS  THE  MONARCH. 

From  Kellogg's  Zoology. 

General  Characters  of  Lepidoptera.  —  The  moths  and 
butterflies  have  two  pairs  of  scaly  wings,  which  are  large 
and  slow  in  motion.  The  parts  of  the  body  are  distinct. 


32  Descriptive  Zoology. 

The  long,  coiled  sucking  tube,  composed  of  the  two  max- 
illae, is  a  noticeable  feature.  The  legs  are  small  and  weak, 
some  forms  having  but  two  pairs,  others  having  the 'anterior 
pair  but  not  using  them. 


ORDER  DIPTERA. 

The  House  Fly. — The  house  fly  has  but  one  pair  of 
developed  wings,  the  second  pair  being  represented  by  a 
pair  of  bodies  resembling  pins,  that  is,  consisting  of  a 
threadlike  stalk  with  a  knob  at  the  end.  They  are  called 
balancers  ;  their  function  is  supposed  to  be  sensory.  When 
the  fly  is  at  rest  the  wings  are  extended  backward  and 
held  horizontally  over  the  back,  lapping  over  each  other  at 
the  inner  borders,  but  are  not  folded,  in  the  strict  sense  of 
that  term;  that  is,  are  not  thrown  into  folds,  as  are  the 
inner  wings  of  the  grasshopper. 

The  mandibles  and  maxillae  are  rudimentary,  and  the 
proboscis  is  composed  mainly  of  the  labial  palps,  which 
are  developed  into  broad  plates,  which  are  thus  adapted 
not  only  for  lapping  but  also  for  rasping.  They  cannot 
bite,  though  they  often  light  on  the  human  skin  to  lap  up 
the  perspiration. 

The  wing  movements  are  very  rapid,  making  as  many  as 
330  vibrations  in  a  second.  The  sound  produced  by  flies 
is  mainly  made  by  the  vibrations  of  the  wings;  but  when 
the  fly  is  held  by  the  wings,  there  is  still  heard  a  faint 
buzzing  noise,  and  this  is  supposed  to  be  due  to  the  pas- 
sage of  air  through  the  spiracles. 

Development  of  the  House  Fly.  —  House  flies  lay  their 
eggs  in  stable  manure,  each  female  laying  about  150  eggs. 
In  favorable  weather,  the  eggs  hatch  in  about  one  day. 


Inead 


Horse  fly 


FIG.  27.  HORSE  FLY,  STRUCTURE  AND  DEVELOPMENT. 

at,  antenna;  la,  labium;  md,  mandible;  mx,  maxilla.  —  From  Hyatt's  Insecta. 


34  Descriptive  Zoology. 

The  legless  larva  is  called  a  maggot.  After  living  in  this 
state  about  a  week,  it  becomes  a  pupa,  remaining  in  its  old 
larval  skin,  which  is  called  a  puparium.  (See  Fig.  27.)  In 
a  week  more  it  emerges  as  a  fly.  There  may  be,  therefore, 
ten  or  a  dozen  generations  in  a  single  summer.  A  small 
number  live  over  winter,  hiding  in  crevices  in  walls  and 
similar  places.  House  flies  are  worse  than  mere  nuisances, 
they  are  spreaders  of  disease.  On  the  other  hand  they 
do  much  good  as  scavengers. 

How  Flies  Crawl.  —  The  fly  has  many  little  hairlike  pro- 
jections on  its  feet.  These  secrete  a  sticky  substance  from 
their  ends,  by  means  of  which  the  fly  adheres  to  smooth 
walls  and  ceilings. 

Other  Kinds  of  Flies.  —  The  stable  flies  closely  resemble  the  house 
flies,  but  have  a  sharp,  piercing  sucking  tube.  They  sometimes  rind 
their  way  into  houses,  especially  on  warm,  rainy  days  in  the  fall.  On 

the  other  hand  many  of  the  flies 
seen  about  stables  are  house  flies. 
The  horseflies  are  well  known, 
the  most  common  being  known  as 
the  "greenhead";  a  still  larger 
form  is  dull  black,  and  in  the  West 
is  called  "  bulldog,11  from  its  size 
and  persistency  ;  still  smaller  than 
either  are  those  with  banded  wings, 
and  these  usually  have  the  wings 
spread  wider  so  that  the  fly  looks 

FIG.  28.    THE  BEE  KILLER.  triangular;  some  of  these  are  called 

u  deer  flies.11    It  is  a  surprise  to  find 

r  rom  Hyatt  s  Insecta. 

the  big  black  horseflies  abundant 

and  annoying  in  the  cold  air  of  the  high  tops  of  the  Rocky  Mountains. 
Among  the  forms  that  annoy  man  and  beast  are  the  black  flies,  or 
midges,  often  swarming  in  the  Adirondacks.  On  account  of  their 
smallness  the  Indians  call  them  "  no-see-ems.11  To  guard  himself 
against  these  pests  the  hunter  and  the  fisher  often  anoint  the  face 
and  the  hands  with  a  mixture  of  tar  and  oil  of  pennyroyal. 


Insecta.  35 

Every  one  has  noticed  the  big  fly  that  occasionally  is  found  in  houses, 
as  it  attracts  attention  by  its  loud  buzzing  and  its  bluish  abdomen. 
It  is  the  blowfly,  that  lays  its  eggs  on  meat.  It  is  a  disgusting  sight 
to  behold  flesh  "  alive  with  maggots,1'  but  when  one  reflects  he  sees 


Breathing  tubes 


Pupa.  Larva. 

FIG.  29.    DEVELOPMENT  OF  THE  MOSQUITO. 

what  a  wise  provision  of  nature  it  is  that  such  decaying  matter  should 
be  so  promptly  and  effectually  disposed  of.  Let  the  hunter  sit  down 
to  eat  his  lunch  of  biscuit  and  meat  in  any  part  of  the  Rocky  Moun- 
tains, and  the  chances  are  that  before  he  has  finished  the  blowflies  will 
have  discovered  the  presence  of  flesh,  and  come  buzzing  around  him. 

The  botfly  lays  its  eggs  on  the  hairs  of  horses1  fore  legs  and  shoul- 
ders. The  horse  gets  them  into  the  mouth  from  scratching  itself  by 
biting,  and  swallows  them.  The  larva  attaches  itself  by  means  of  hooks 
to  the  inner  wall  of  the  stomach.  Later  it  passes  on  through  the  intes- 
tine, and  the  pupa  completes  its  development  in  the  dung. 

"  Skippers  "  are  the  larvae  of  black  flies,  about  half  the  size  of  the 
house  fly,  that  lay  their  eggs  on  cheese,  ham,  and  bacon.  Bills  received 
from  packing  houses  often  specify  that  they  do  not  guarantee  their  goods 
against  skippers. 

There  are  also  flies  that  injure  plants.  Among  these  the  Hessian  fly 
is  well  known.  The  larva  is  to  be  found  between  the  sheath  of  a  blade 
of  wheat  and  the  stalk,  where  it  does  its  damage.  There  is  also  a 
"  wheat  midge  "  which  causes  considerable  loss.  Nearly  every  one  must 
have  noticed  on  the  ends  of  willow  twigs  a  gray  cone-shaped  growth. 
This  is  caused  by  the  developing  larva  of  the  "pine  cone"  gall  gnat. 

The  Mosquito.  —  The  mosquito  lays  its  eggs  on  stagnant  water.  The 
larvae  are  known  as  "  wrigglers,"  and  their  well-known  habits  justify  the 


36  Descriptive  Zoology. 

name.  The  larva  breathes  by  a  tube  at  the  hinder  end  of  the  body. 
The  pupa  is  also  active ;  it  breathes  air  through  two  tubes  which  grow 
out  of  the  thorax.  The  piercing  and  sucking  tube  of  the  adult  consists 
of  several  mouthpieces  which  fit  snugly  together.  Only  the  female  bites. 
She  is  a  cheerful  individual,  singing  as  she  goes  about  her  work.  Some 
excellent  authorities  believe  that  mosquitoes  are  the  chief  agents  in  intro- 
ducing the  germs  of  malaria  into  the  human  system.  Pouring  kerosene 
on  the  water  in  which  mosquitoes  are  breeding  will  kill  them,  and  this 
is  probably  a  more  practical  method  of  reducing  their  number  than  might 
be  at  first  supposed,  for  kerosene,  like  any  other  oily  substance  when  on 
water,  spreads  out  in  an  exceedingly  thin  film,  a  little  of  it  going  a  long 
way. 

Diptera.  —  This  order  of  insects  receives  its  name  from 
the  fact  that  its  members  have  but  two  wings,  as  seen  in 
the  flies  and  mosquitoes.  The  life  history  of  the  house  fly 
is  fairly  typical.  The  knobbed  balancers  (rudimentary 
hinder  wings)  are  called  "halteres." 


ORDER   COLEOPTERA. 

The  May  Beetle.  —  This  brown  fellow  is  well  known,  but 
more  commonly  under  the  incorrect  name  "June  bug." 
You  will  hardly  need  to  hunt  for  a  specimen,  for  if  you 
leave  your  window  open  as  you  sit  by  your  lamp  on  an 
evening  in  May  or  June,  he  will  come  to  you.  Instead  of 
picking  him  up  and  throwing  him  out  of  the  window,  as  you 
have  been  in  the  habit  of  doing,  lay  down  your  book  and 
study  him,  for  he  will  teach  you  more  about  himself  than 
you  could  possibly  learn  from  any  book  in  the  same  length 
of  time.  At  his  best  he  is  a  poor  flier,  and,  bewildered  by 
the  glare  of  light,  he  is  more  clumsy  than  ever ;  if  he  bumps 
against  the  lamp  and  falls  upon  the  table,  you  will  have  a 
good  look  at  him.  Note  the  order  in  which  the  legs  are 
moved  in  crawling.  Try  to  pick  him  up  and  find  how  he 


antenna 
mandi      ^ 
maxilla  t4x      JJ 


Hay-beetle 


FIG.  30.    THE  MAY  BEETLE,  STRUCTURE  AND  DEVELOPMENT. 

From  Hyatt's  Insecta. 


38  Descriptive  Zoology. 

holds  on  so  well.  Observe  another  one  flying,  —  see  how 
he  holds  the  wing  covers  up  and  out  at  the  sides.  As  soon 
as  he  lights,  see  how  these  wing  covers  come  down  over 
the  membranous  flying  wings,  which  at  first  project  behind 
the  wing.  Watch  him  tuck  the  wings  under  the  wing  covers ; 
can  you  tell  how  he  does  it  ?  After  the  membranous  wings 
have  been  withdrawn  from  sight,  pick  him  up  and  note 
that  the  wing  covers  meet  in  a  straight  line  along  the 
middle  of  the  back,  entirely  concealing  the  true  wings. 
Note  also  the  large  prothorax.  The  head  is  small,  but  has 
strong  mandibles  and  two  pairs  of  maxillae.  The  enlarged 
ends  of  the  antennae  consist  of  a  series  of  leaflike  plates, 
giving  the  name  to  a  large  group,  —  the  Lamellicorn 
beetles.  Watch  him  as  he  starts  to  fly  again.  In  order 
to  give  the  flying  wings  free  play,  the  wing  covers  must  be 
held  well  up  and  forward.  In  this  position  they  make  con- 
siderable resistance  to  flight,  and  it  is  easy  to  see  that  this 
kind  of  insect  cannot  be  a  first-class  flier. 

These  beetles  sometimes  do  considerable  damage,  by 
eating  the  leaves,  especially  of  the  cherry.  In  the  early 
evening  one  may  see  swarms  of  May  beetles  and  later  hear 
them  buzzing  about  the  foliage. 

The  eggs  are  laid  in  the  ground  and  hatch  out  into 
white  "grubs."  Every  boy  knows  them  well  and  uses 
them  for  bait,  and  often  he  learns  that  the  blackbirds 
know  enough  to  follow  the  plow  and  pick  up  the  grubs 
that  are  left  in  the  furrow.  The  grub  usually  has  a  dark 
head,  with  a  white  body,  the  first  three  segments  bearing 
each  a  pair  of  jointed  legs  that  correspond  to  the  three 
pairs  of  legs  of  the  adult  beetle.  The  hinder  part  of  the 
body  is  often  dark  from  the  dirt  that  has  been  eaten. 
Every  one  knows  how  they  lie  curled  up  and  in  the  ground; 
they  generally  rest  on  their  backs.  They  often  do  great 


Insecta. 


39 


injury  by  eating  the  roots   of  grasses,  strawberry  plants, 
corn,  grain,  and  other  plants.    The  larva  lives  in  the  ground 


e 

FIG.  31.  THE  COLORADO  POTATO  BEETLE  AND  ITS  DEVELOPMENT. 

a>  eggs;  3,  larvae;  c,  pupa  (underground);  d,  adult;  e,  wing  cover;  f,  leg. 
From  Hyatt's  Insecta. 

two  or  three  years.     The  last  of  its  stay  is  passed  in  a 
pupa  state,  when  it  is  inactive,  lying  in  a  smooth,  oval 

cavity  it  has  made  for  itself. 

The  Colorado  Potato  Beetle. —This  is 
too  well  known  to  need  description.  It  is 
a  native  of  the  Rocky  Mountain  region, 
where  it  lived  on  a  species  of  Solanum  (to 
which  genus  the  potato  belongs)  ;  when 
the  potato  began  to  be  cultivated  near  its 
home,  the  beetle  transferred  to  the  new 
plant,  and,  starting  in  1859,  it  spread  east- 
ward till  it  reached  the  Atlantic  coast  in 
1874. 

The  Ground  Beetles.  —  Among  the  most 
common  of  our  beetles  are  the  ground 
beetles,  to  be  found  under  logs,  boards,  and  stones,  or  running  about  on 


FIG.  32.  COMMON  GROUND 
BEETLE. 

From  Hyatt's  Insecta. 


40  Descriptive  Zoology. 

the  ground  in  the  summer  and  fall.  The  caterpillar  hunter  has  green 
wing  covers  and  is  over  an  inch  long.  The  fiery  hunter  has  on  the 
wing  covers  rows  of  red  or  copper-colored  spots. 

The  Tiger  Beetles.  —  These  beetles  get  the  name  from  their  active 
predaceous  habits,  as  well  as  from  their  bright-colored  and  yellow-barred 
wing  covers.  They  run  actively  and  fly  well  for  beetles.  They  are 
often  to  be  seen  on  the  ground,  especially  on  sand  along  streams.  When 
you  attempt  to  capture  one  it  may  remain  quiet  till  you  get  near  it, 
when  it  darts  away,  flying  a  short  distance,  and  usually  lights  with  its 
head  toward  you. 

The  Borers.  —  There  are  many  beetles  whose  larvae  bore  into  trees, 
where  they  do  great  damage.  Among  these,  perhaps  the  locust  borer 


FIG.  33.    HICKORY  TREE  BORER;  LARVA,  PUPA,  AND  ADULT. 

From  Hyatt's  Insecta. 

and  the  painted  hickory  borer  are  found  as  frequently  as  any.     The 
woodpeckers  do  good  service  in  destroying  these  grubs. 

The  Stag  Beetles.— Many  children  know  these  beetles  as  "pinch 
bugs."  The  large,  incurved  mandibles  are  very  characteristic.  The 
larvae  usually  live  in  decaying  wood. 

The  Dung  Beetles.  —  No  boy  or  girl  who  has  spent  much  time  in  the 
country  has  missed  seeing  these  odd  beetles,  called  "tumble-bugs." 
On  the  way  to  and  from  the  district  school  the  child  meets  the  pairs 
of  beetles  rolling  the  big  ball  that  they  have  made  from  the  drop- 
pings of  horses  and  cattle.  It  is  interesting  to  see  them,  one  pushing 
and  one  putting;  as  he  patiently  follows  and  watches  them,  he  sees 
them  at  last  bury  the  ball.  Later  the  child  learns  that  the  female  lays 
eggs  in  the  ball,  which  the  larvae  consume  as  food. 

The  "Weevils."  —  Some  of  these  are  small  beetles,  not  more  than 
one  fifth  of  an  inch  long.  They  lay  their  eggs  on  the  pea  pods ;  the 


Insecta.  41 

larvae  bore  their  way  into  the  pea,  and  eat  out  to  the  skin  through 
which  the  adult  easily  makes  his  way  when  ready  to  emerge. 

Blister  Beetles.  —  A  large  family  of  beetles  has  a  blistering  substance 
which  is  used  in  making  blistering  plasters.  The  "Spanish  fly11  be- 
longs to  this  group.  One  of  the  most  common  of  our  blister  beetles  is 
a  black  fellow  abundant  on  goldenrod  flowers. 

Carrion  Beetles.  —  These  usually  have  club-shaped  antennae.  The; 
are  well  known,  as  both  the  larvae  and  the  adults  feed  on  decaying 
flesh.  Some  of  these  beetles  are  called  "sexton  beetles11  from  the  fact 
that  they  bury  small  animals. 

The  Rove  Beetles.  —  These  are  odd  forms,  with  short  wing  covers, 
which  hardly  conceal  half  of  the  abdomen.  This  is  long  and  flexible, 
and  is  often  carried  turned  up  as  if  threatening  to  sting,  which  it  has  no 
power  to  do.  4 

The  Ladybugs.  —  All  children  who  live  in  the  country  know  these 
hemispherical  beetles,  with  their  smooth  and  often  brightly  colored  and 
spotted  backs.  Most  of  them  are  predaceous,  and  one  of  the  greatest 
triumphs  of  economic  entomology  was  the  introduction  of  a  species  of 
ladybug  from  Australia  into  California,  where  it  largely  checked  the 
ravages  of  a  scale  insect,  which  was  making  havoc  with  the  fruit  trees. 

The  Carpet  Beetles.  —  Some  of  these  destroy  carpets.  Others  are 
the  greatest  pests  of  museums,  destroying  the  stuffed  specimens.  The 
best  remedy  is  bisulphide  of  carbon,  whose  fumes  are  fatal  to  eggs, 
larvae,  and  adults. 

The  Click  Beetles.  —  Boys  know  them  as  "spring  beetles,11  "snap- 
ping bugs,11  "  skipjacks,11  etc.  Lay  one  on  its  back,  and  soon  it  gives  a 
spring,  with  a  click,  that  raises  it  perhaps  several  inches.  If  it  lights 
on  its  back,  it  soon  tries  again.  These  beetles,  like  many  others,  "  play 
possum.11  Their  larvae  are  "  wire  worms,11  and  do  great  damage,  eat- 
ing the  roots  of  corn,  grain,  grasses,  and  other  plants.  One  of  our 
largest  click  beetles,  the  eyed  elater,  is  gray,  and  has  on  the  prothorax 
two  large  black  spots  resembling  eyes. 

The  Snout  Beetles.  —  These  beetles  (the  true  weevils)  are  very  odd 
in  having  the  head  prolonged  into  a  long  beak,  sometimes  longer  than 
the  body.  Most  of  these  are  known  as  curculios.  They  bore  a  hole 
with  the  end  of  the  snout,  deposit  the  egg,  and  then  push  the  egg  to 
the  bottom  of  the  hole  with  the  snout.  They  destroy  many  fruits  and 
nuts. 


42  Descriptive  Zoology. 

The  Fireflies.  —  These,  too,  are  beetles.  Children  do  not  need  to 
be  told  that  they  emit  light,  and'  the  most  learned  scientist  cannot  tell 
just  how  the  light  is  produced.  The  females  of  some  fireflies  are  wing- 
less, and  are  called  "  glowworms.1' 

Water  Beetles.  —  Not  least  interesting  among  beetles  are  the  water 
beetles.  We  shall  notice  three  kinds.  First,  the  whirligig  beetles, 
which  nearly  everybody  has  observed  on  the  surface  of  the  water,  whirl- 
ing round  and  round  in  swarms.  Like  the  other  water  beetles,  they 
have  a  flattened  body,  and  the  hinder  legs  are  paddle-shaped.  The 
whirligig  beetles  occasionally  dive.  They  have  each  eye  divided  into 
two  parts,  one  of  which  looks  up  and  the  other  down,  so  that  one  would 
s.iy  they  had  two  pairs  of  eyes. 

The  predaceous  diving  beetles  have  oval  bodies,  somewhat  wider 
behind.  They  are  more  abundant  in  stagnant  water.  When  at  rest 
they  come  to  the  surface  and  remain  with  the  head  down  and  the  tip  of 
the  abdomen  projecting  into  the  air.  Like  the  water  bugs,  they  breathe 
by  taking  air  under  the  wings,  and  when  a  new  supply  is  needed  they 
again  come  to  the  surface.  The  spiracles  are  on  the  upper  surface  of 
the  abdomen.  They  are  very  voracious,  and  eat  other  insects  and  even 
small  fishes.  The  larvae  are  spindle-shaped,  with  sharp,  incurved 
mandibles,  and  are  known  as  "water  tigers"  on  account  of  their  fierce- 
ness. Both  larvae  and  adults  may  be  kept  and  fed  on  meat. 

The  water  scavenger  beetles  are  elliptical.  They  do  not  breathe  as 
do  the  predaceous  water  beetles,  but  come  to  the  surface  head  up  and 
take  air  under  the  body,  where  it  is  carried  as  a  film,  which  gives  a  sil- 
very gleam  when  seen  from  beneath.  They  are  supposed  to  feed  mainly 
on  decaying  vegetable  matter,  but  some  are  known  to  catch  live  insects 
and  eat  them.  They  may  be  distinguished  from  the  predaceous  water 
beetles  by  their  shape,  and  by  a  long,  sharp  spine  that  projects  back- 
ward from  the  under  surface  of  the  thorax.  Catch  one  of  these  beetles 
by  one  of  the  hind  legs  and  you  will  probably  find  out  the  use  of  this 
spine.  Though  all  these  beetles  have  the  power  of  flight,  they,  do  not 
usually  try  to  escape  from  ajar  of  water.  It  is  easy  to  catch  them  by 
scooping  in  ponds  with  a  dip  net.  They  may  be  kept  in  glass  jars 
(candy  jars  are  very  convenient),  and  watched  from  below  as  well  as 
from  above.  If  they  have  no  solid  surface  on  which  to  crawl,  they  are 
not  likely  to  get  away.  It  would  seem  that  they -cannot  start  to  fly 
from  the  surface  of  the  water,  but  must  have  some  solid  object  from 
which  to  rise  into  the  air. 


Insecta.  43 

Coleoptera.  —  The  beetles  are  called  Coleoptera,  mean- 
ing sheath-winged,  from  the  hard,  horny  wing  covers. 
The  hind  wings  are  membranous,  and  are  usually  consid- 
erably longer  than  the  wing  covers.  To  enable  the  beetle 
to  protect  them  there  is  a  joint  in  the  anterior  edge  of  the 
wing  so  that  it  can  be  folded  crosswise  as  well  as  length- 
wise. This  is  accomplished  by  moving  the  abdomen  down- 
ward and  backward,  then  upward  and  forward  to  draw  the 
wing  under  the  covers.  Some  beetles  lack  true  wings  and 
are  unable  to  fly.  The  mouth  parts  are  fitted  for  biting. 

All  insects  have  chitin  in  the  skin  to  stiffen  it,  but  the 
beetles  have  this  most  fully  developed,  and  are  the  hardest 
and  firmest  bodied  of  insects.  This  is  in  keeping  with  their 
mode  of  life,  as  many  of  them  crawl  into  crevices,  under 
stones,  logs,  etc.  They  are  the  strongest  of  insects,  and 
the  load  they  can  carry,  in  proportion  to  their  weight,  is 
marvelous.  Beetles  have  compound  eyes,  but  almost  always 
lack  the  simple  eyes  that  are  present  in  most  insects. 

As  the  under  surface  of  the  abdomen  is  subject  to  fre- 
quent pressure,  it  needs  to  be  hard  and  unyielding.  How, 
then,  can  respiration  be  effected?  It  is  secured  by  having 
the  upper  surface  of  the  abdomen  more  soft  and  flexible ; 
by  the  in-and-out  movement  of  this  region  the  air  is  taken  in 
and  sent  out  through  the  spiracles,  which,  except  in  water 
beetles,  may  usually  be  seen  along  the  abdomen. 

In  a  former  chapter  we  saw  how  the  dragon  fly  would 
have  to  change  if  he  were  to  assume  the  life  of  a  locust. 
Go  a  step  farther  and  it  will  be  evident  that  the  beetle, 
forcing  his  way  into  crevices  and  into  narrow  places,  has 
acquired  the  hard,  smooth  body  which  he  requires  to  fit 
him  for  such  a  life. 

There  is  great  variety  in  the  habits  of  beetles ;  they  live 
in  air  and  in  water;  are  carnivorous  and  herbivorous;  some 


44  Descriptive  Zoology. 

are  parasitic ;  the  larvae  are  found  in  the  earth,  in  decay- 
ing wood,  in  the  living  wood  of  hard  trees,  in  manure,  in 
carrion,  in  fruits  and  seeds. 

Many  are  injurious;  others  are  beneficial,  as  the  lady- 
bugs,  which  destroy  injurious  insects. 

ORDER   HYMENOPTERA. 

The  Honeybee.  —  Our  honeybee  is  of  European  origin, 
and  has  long  been  domesticated.  Occasionally  escaped 
swarms  live  in  a  wild  state.  The  three  parts  of  the  body, 
namely,  head,  thorax,  and  abdomen,  are  very  distinct ; 
but  it  should  be  noticed  that  the  prothorax,  instead  of 
being  immovably  connected  with  the  rest  of  the  thorax,  as 
in  the  fly  and  many  other  insects,  is  movable.  Another 
feature,  peculiar  among  insects,  is  the  transferring  of  one 
segment  from  the  abdomen  to  the  thorax,  —  what  appears 
to  be  the  last  segment  of  the  thorax  being  really  the  fore- 
most segment  of  the  abdomen.  The  second  segment  of 
the  abdomen  (apparently  the  first)  is  slender,  and  allows 
the  abdomen  to  be  bent  sharply  forward  under  the  thorax ; 
and  nearly  every  one  has  learned,  in  a  way  that  he  will  not 
forget,  how  and  why  the  bee  does  this. 

The  two  pairs  of  wings  are  membranous,  the  hind  pair 
being  much  smaller  than  the  anterior.  Along  the  front 
margin  of  the  hind  wings  is  a  row  of  hooks  which  catch  on 
a  ridge  at  the  hind  edge  of  the  front  wings,  so  that  in  flight 
the  two  wings  work  as  one,  —  in  fact  until  the  wings  are 
unhooked  there  seems  to  be  but  one  pair. 

The  mouth  parts  are  peculiar.  In  most  insects  the  mouth 
parts  are  fitted  either  for  biting  or  for  sucking.  In  the  bee 
we  find  both  sorts  of  structures.  Mandibles  are  present, 
and  sometimes  are  strongly  developed.  But  the  food  of 


head 


Honey-bee 


FIG.  34.    THE  HONEYBEE,  STRUCTURE  AND  DEVELOPMENT, 

From  Hyatt's  Insecta. 


46  Descriptive  Zoology. 

the  honeybee  is  liquid,  and  the  tongue  is  the  conspicuous 
organ.  The  two  nlaxillae,  with  the  two  labial  palps,  form 
the  sucking  tube,  within  which  the  cylindrical  tongue  moves 
up  and  down. 

The  antennae  are  like  an  arm  bent  at  right  angles  at  the 
elbow.  The  pollen  "  basket "  (see  Fig.  34)  is  on  the  out- 
side of  the  tibia  of  the  hind  legs  of  the  workers,  and  is 
simply  a  flattened  segment  surrounded  by  stiff  hairs.  The 
sting  is  a  modified  ovipositor,  consisting  of  several  pieces 
closely  fitting  together,  constituting  a  tube,  through  which 
the  poison  is  conveyed  from  the  poison  gland  within  the  tip 
of  the  abdomen. 


FIG.  35.    HONEYBEE. 

a,  drone  or  male;  b,  worker  or  infertile  female;  c ,  queen  or  fertile  female. 
From  Jordan  and  Kellogg's  Animal  Life. 

Kinds  of  Bees  in  a  Hive.  —  There  are  three  forms  of 
honeybees,  —  the  queen  or  female,  the  drones  or  males, 
and  the  workers,  which  are  undeveloped  females.  There 
is  but  one  queen  in  a  hive  most  of  the  time,  and  compara- 
tively few  drones,  the  great  majority  being  workers.  The 
average  hive  consists  of  from  twenty-five  thousand  to  thirty- 
five  thousand  bees,  but  there  may  be  as  many  as  fifty  thou- 
sand. The  drones  have  broad,  blunt  bodies,  and  have  no 
stings ;  and  may  be  further  distinguished  by  their  large 
eyes,  which  make  up  most  of  the  head.  They  may  be  found 
in  the  hive  in  the  early  summer,  but  after  the  swarming 


Insecta.  47 

season  is  over  they  are  driven  out  or  killed  by  the  workers. 
The  workers  are  the  smallest  of  the  three  kinds,  and  are 
provided  with  " pollen  baskets"  and  stings.  The  queen  is 
larger  than  the  workers,  and  has  a  long,  pointed  abdomen. 
She  has  2  sting,  but  never  uses  it  except  against  a  rival 
queen.  The  average  life  of  a  worker  is  about  five  weeks. 
Workers  may  live  eight  months,  while  a  queen  has  been 
known  to  live  five  years. 

The  Work  of  the  Hive.  —  As  indicated  in  the  name,  the 
management  of  the  hive  falls  chiefly  on  the  workers.  In  the 
first  place,  the  workers  make  honey.  They  gather  nectar 
from  flowers ;  this  is  taken  into  the  honey  stomach,  but 
not  mainly  for  the  sustenance  of  the  worker.  It  is  trans- 
ferred to  the  cells,  loses  some  water  by  evaporation,  and 
becomes  honey.  The  workers  make  the  wax  from  which 
the  comb  is  made.  The  wax  is  a  secretion  from  the  glands 
on  the  under  surface  of  the  abdomen.  When  wax  is  needed 
a  large  number  of  workers  gorge  themselves  with  honey 
and  hang  like  a  curtain,  clinging  to  each  other,  remaining 
quiet.  As  the  wax  exudes  from  the  glands,  other  workers 
gather  it  and  construct  the  comb.  The  economy  of  mate- 
rial is  well  known,  but  the  cells  are  not  always  mathemati- 
cally exact,  as  is  commonly  supposed. 

The  workers  also  collect  a  gummy  substance  from  buds, 
which  forms  propolis,  or  "  bee  glue,"  with  which  they 
cement  crevices  and  make  similar  repairs.  Pollen  is  also 
gathered  in  a  "  basket "  on  each  hind  tibia.  Of  this  pollen 
"bee  bread  "  is  made  for  feeding  the  young. 

Development.  —  For  the  rearing  of  the  young  special 
cells  are  made  which  constitute  the  "brood  comb."  This 
brood  comb  may  be  afterward  used  for  storing  honey.  The 
queen  deposits  an  egg  at  the  bottom  of  each  cell,  and  after 
they  hatch,  the  larvae  are  fed  by  the  workers  till  ready  to 


48 


Descriptive  Zoology. 


Larv 


go  into  the  pupa  state,  when  the  cell  is  capped  over  till 

the  pupae  transform  into  adult  (or  imago)  bees. 

The  drones,  being  larger  than  the  workers,  are  developed 

in  larger  cells.     Queen  cells  are   larger  than  other  cells. 

At  the  season  of  the  year  when   the   bees  gitfe   regular 

attention  to  rearing  queens, 

Egg  ^-^r^^^^^^^          tne  queen  cells  are  usually 

built  at  the  bottom  or  ends 
of  the  comb.  But  if  the 
bees  are  obliged  to  produce 
a  queen  out  of  the  regular 
swarming  season,  the  queen 
cells  are  made  by  tearing 
out  the  partitions  and  com- 
bining three  cells  into  one, 
which  is  built  out  and  hangs 
vertically  in  front  of  the 
comb.  In  the  egg  state 
there  is  no  difference  be- 
tween  the  queen  and  the 


Queen 
cell 


FIG.  36.   CELLS  CONTAINING  EGGS,  LAR- 
v*:,  AND  PUP,*  OF  THE  HONEYBEE. 

The  large,  irregular  cells  are  queen  cells.-  From     Worker,    but    the    larva    that 
Jordan  and  Kellogg's  Animal  Life.  jg   ^  become  a  queen  js  f  e(J 

on  specially  prepared  food.  In  the  early  part.  of  the  sum- 
mer several  queen  cells  are  made  ;  as  soon  as  a  new  queen 
is  hatched  the  old  queen  tries  to  kill  her  ;  but  the  workers 
protect  the  new.  queen,  and  the  old  queen,  followed  by  a 
part  of  the  workers,  departs  to  establish  a  new  colony,  and 
this  is  called  "  swarming."  If  a  number  of  new  queens  are 
hatched  at  the  same  time,  they  may  fight  for  leadership, 
and  the  one  survivor  rules  supreme.  Or,  often,  several 
young  queens  depart  with  a  swarm. 

The  queens  that  are  thus  killed  are  carried  out  by  the 
workers,  and  they  do  the  same  for  any  that  die  in  the  hive. 


Insecta.  49 

All  dirt  and  rubbish  are  carefully  removed,  the  hive  being 
a  model  of  neatness. 

In  warm  weather  a  number  of  workers  may  be  observed 
stationed  at  the  entrance,  fanning  vigorously  with  their 
wings ;  they  do  this  to  ventilate  the  hive. 

Bumblebees.  —  The  queen  is  the  only  one  of  a  colony  that  lives 
over  the  winter.  Selecting  some  convenient  place  for  a  nest,  usually  an 
old  nest  of  a  field  mouse,  she  gathers  a  mass  of  pollen  and  lays  some 
eggs  upon  it.  As  the  eggs  hatch  out  the  larvae  eat  into  the  pollen,  and 
when  fully  developed  spin  silken  cocoons  for  themselves.  After  these 
cocoons  have  served  as  cradles  they  are  strengthened  with  wax  and 
used  for  storing  honey.  Every  country  boy  has  robbed  the  nests  of  the 
bumblebee ;  he  likes  the  honey  and  is  willing  to  pay  the  price  for  it. 
Nearly  the  whole  colony  of  bumblebees  may  be  captured  by  pouring 
water  into  the  nest,  which  renders  them  unable  to  fly ;  or  if  a  jug  partly 
filled  with  water  be  set  near  the  nest,  when  they  are  disturbed  they 
usually  enter  the  jug,  and,  getting  into  the  water,  are  easily  taken ;  or 
the  whole  colony  may  be  chloroformed.  Being  larger  than  the  honey- 
bee, they  offer  some  advantages  for  study. 

Other  Bees.  —  The  honeybees  and  bumblebees  are  called  social  bees 
in  distinction  from  other  kinds  of  bees  that  lead  a  solitary  life.  Among 
the  solitary  bees  is  the  carpenter  bee,  that  tunnels  into  wood,  sometimes 
a  foot  or  more.  Some  bees  cut  out  circular  pieces  of  leaves  with  which 
to  line  their  holes.  Others  dig  holes  in  the  ground ;  some  mine  into 
the  sides  of  banks,  one  group  of  the  mining  bees  being  called  the 
"  short-tongued  "  bees.  There  are  also  several  parasitic  bees. 

Wasps.  —  As  with  the  bees,  some  of  the  wasps  are  social,  while 
others  are  solitary.  In  colonies  there  are  three  kinds  of  individuals, 
males,  females,  and  workers,  all  winged.  The  wings,  unlike  those  of 
bees,  are  folded  into  plaits,  as  in  a  fan.  They  build  nests  either  in  the 
ground  or  on  trees  and  buildings.  Nearly  everybody  has  seen  the 
large  nests  suspended  from  trees,  about  the  size  and  shape  of  a  football ; 
and  perhaps  many  have  vivid  recollections  of  the  warm  reception  they 
received  when  they  knocked  abruptly  at  the  door  of  this  lively  commu- 
nity. The  hornet,  or  yellow  jacket,  need  not  be  described  to  a  country 
lad.  "  Eternal  enmity1'  is  sworn  between  them,  and  each  knows  there 
is  no  use  of  showing  a  white  flag.  Still,  the  skillful  teacher  may  capture 


50  •  Descriptive  Zoology. 

the  entire  colony  by  quietly  slipping  an  insect  net  over  the  nest  and 
tying  the,  net  to  inclose  them.  Later  a  hole  may  be  made  in  the  tip  of 
the  net,  and  a  single  hornet  at  a  time  may  be  allowed  to  pass  under  a 
tumbler  inverted  on  a  plate.  After  being  kept  awhile  they  will  be 
hungry,  and  if  a  drop  of  sugar  water  be  introduced,  the  proud  captive 
will  not  hesitate  to  let  his  enemies  see  how  he  eats.  The  entrance  to 
these  nests  is  below,  while  within  are  horizontal  combs.  The  wasps 
make  the  nests  out  of  wood  fibers,  which  they  tear  off  stumps,  fences, 
and  unpainted  buildings.  They  chew  these  fibers  into  a  pulp  and  make 
a  coarse  gray  paper.  They  probably  are  the  original  paper  makers. 

Another  wasp  builds  a  single  layer  of  comb,  which  is  held  horizon- 
tally under  some  protecting  object  by  a  narrow  stalk,  the  comb  not 
being  surrounded  by  a  case  as  with  the  yellow  jackets.  The  wasps 
that  make  nests  in  the  ground  also  make  paper  to  line  the  nest. 

Among  the  solitary  wasps  some  are  diggers,  and  it  is  interesting  to 
see  one  of  them  digging  a  hole,  throwing  the  dirt  back  as  it  digs  very 
much  as  a  dog  does.  Others  make  tunnels  into  the  stems  of  plants, 
where  the  young  are  reared. 

The  mud  dauber  wasps  are  slender-waisted,  and  wear  a  suit  of  shiny 
dark  blue.  -  They  have  the  habit  of  nervously  jerking  their  wings. 
They  are  often  seen  lighting  on  the  mud  about  horse  troughs,  where 
they  are  gathering  mud  for  their  nests.  They  make  a  nest  of  several 
cells,  in  which  the  eggs  are  deposited.  We  see  these  cells  on  rafters, 
under  eaves,  etc. 

Some  wasps  store  the  cells  with  spiders  and  insects  for  the  larva  to 
feed  on  till  it  emerges.  Often  the  insect  is  stung  so  as  to  paralyze,  but 
not  quite  kill  it. 

Ants.  —  Here,  again,  we  have  a  communistic  society  with  perhaps  a 
still  more  perfect  division  of  labor.  The  males  and  females  at  first 
have  wings,  but  the  males  are  short-lived,  and  the  females  soon  bite  off 
their  wings.  The  work  is  done  by  the  workers,  who  are  wingless. 
Some  make  a  nest  in  the  ground,  while  others  tunnel  into  decaying 
wood.  In  a  disturbed  nest  we  sometimes  see  the  workers  carrying 
eggs.  The  large  white  objects  which  they  carry  are  cocoons.  Ants  are 
very  strong  for  their  size  and  do  a  variety  of  work.  They  care  for  the 
larvae,  protect  the  nest  from  invasion  by  enemies ;  some  species  make 
slaves  (and  it  is  interesting  to  note  that  the  masters  are  light-colored 
and  the  slaves  dark).  They  keep  cows  (aphides)  from  which  they  get 
a  sweet  liquid  (honeydew),  and  some  build  a  covsr  for  their  herds 


Insecta.  51 

(cow  sheds).  In  some  forms  the  masters  are  so  dependent  upon  their 
slaves  that  they  perish  unless  cared  for  by  them.  Some  of  the  ants  that 
keep  the  plant  lice  as  cows  are  injurious  through  the  action  of  the  plant 
lice,  which  feed  on  the  roots  of  corn  and  other  plants.  The  ants  carry 
the  plant  lice,  or  their  eggs,  into  holes  in  the  ground  where  they  survive 
the  winter,  which  they  probably  would  not  otherwise  be  able  to  do. 
Yellow  ants  often  invade  houses,  making  a  nest  within  a  wall  where  it 
is  almost  impossible  to  dislodge  them;  these  are -often  called  "red 
ants."  Though  fond  of  sweets,  ants  are  almost  omnivorous. 

Other  Hymenoptera.  —  Among  the  other  Hymenoptera  we  may  notice 
the  sawflies  whose  leaf-eating  larva?  are  known  as  the  rose  slug,  pear 
tree  slug,  currant  worm,  etc.  Various  forms  of  Hymenoptera  sting  their 
eggs  into  the  stems  and  leaves  of  plants.  Around  the  egg  is  formed  a 


FIG.  37.    LARVA  OF  A  HAWK  MOTH,  WITH  COCOONS  OF  A  PARASITIC  ICH- 
NEUMON FLY. 

From  Kellogg's  Zoology. 

swelling  known  as  a  gall  In  this  the  larva  develops,  finally  eating  its 
way  out.  There  are  many  kinds  of  galls,  and  the  entomologist  knows 
the  kind  of  insect  from  the  characteristic  form  of  the  gall,  and  the  adult 
insects  are  known  as  "gallflies.1' 

The  ichneumon  flies  have  an  ovipositor  consisting  of  long,  slender 
(usually  three)  threads,  by  means  of  which  the  eggs  are  deposited, 
usually  in  the  trunks  of  trees,  where  these  larvae  prey  on  the  larvae  of 
other  boring  insects. 

In  the  fall  one  occasionally  sees  a  sluggish  caterpillar  covered  with 
little  oval  bodies  resembling  eggs ;  examined  more  closely,  these  little 
bodies  are  seen  to  have  a  silky  finish ;  they  are  the  cocoons  of  a  para- 


52  Descriptive  Zoology. 

site.  A  group  of  parasitic  Hymenoptera  (the  Braconids)  deposit  their 
eggs  on  the  caterpillar ;  the  little  larvae  bore  their  way  into  the  big 
larvae,  and  after  consuming  the  tissues  of  the  caterpillar,  eat  their  way 
out  and  add  insult  to  injury,  attaching  their  cocoons  to  the  outside  of 
the  skin.  Sometimes  the  chrysalid  of  a  cabbage  butterfly  fails  to  trans- 
form, and  a  hole  may  be  discovered  where  the  adult  "  Braconids  "  have 
made  their  escape. 

Characteristics  of  Hymenoptera.  —  The  Hymenoptera 
have  two  pairs  of  membranous  wings,  the  hind  pair  being 
smaller  than  the  front.  The  mouth  parts  are  fitted  both 
for  biting  and  for  sucking.  The  female  usually  has  a 
sharp  ovipositor,  which  in  many  cases  is  used  simply  as  a 
sting.  Development  indirect. 

General  Characteristics  of  Insects.  —  i.  Insects  have  a 
segmented  external  skeleton,  i.e.  consisting  of  a  series  of 
rings.  2.  These  rings  are  grouped  in  three  sets,  head, 
thorax,  and  abdomen.  The  head  bears  one  pair  of  an- 
tennae. The  thorax  bears  three  pairs  of  legs  and  usually 
two  pairs  of  wings.  The  abdomen  does  not  usually  have 
jointed  appendages.  3.  Insects  have  air  tubes,  branching 
through  the  thorax  and  abdomen,  by  which  they  breathe. 

Harm  done  by  Insects.  —  i.  They  destroy  crops,  and  the 
damage  to  our  field  and  garden  produce  is  almost  beyond 
computation.  2.  They  convey  disease  both  by  getting  on 
diseased  matter  and  conveying  it  to  our  food,  and  also  by 
introducing  disease  germs  in  biting  (mosquito).  3.  They 
injure  stock  (flies,  mosquitoes,  botflies,  etc.).  4.  They 
injure  buildings  (ants  and  white  ants).  5.  They  are  often 
annoying,  when  not  injurious,  to  man. 

^  Good  done  by  Insects.  —  They  benefit  us  (i)  by  making 
silk;  (2)  by  making  honey;  (3)  by  furnishing  material 
for  making  ink  (galls);  (4)  furnish  dyestuff  (cochineal); 
(5)  they  are  used  in  medicine  (blister  beetles);  (6)  their  use 


Insecta. 


53 


in  fertilizing  flowers  is  unknown  to  many,  but  is  essential 
to  man  in  certain  crops ;  (7)  they  serve  as  scavengers  (flies, 
beetles,  maggots,  etc.);  (8)  many  kinds  are  very  useful  in 
killing  injurious  insects,  as  ichneumon  flies  that  destroy 
borers,  ladybugs  that  eat  scale  insects,  etc. 

On  the  whole  it  would  be  difficult  for  a  jury  to  say 
whether  insects  do  more  harm  than  good ;  and  it  is  per- 
haps best  to  regard  them  as  having  their  place  in  the 
world  to  fill.  And  yet  we  must  not  submit  tamely  to  their 
ravages,  for  we  may  outwit  the  robbers  and  turn  other 
robbers  against  them.  We  should  make  it  a  study  to  turn 
insects,  as  well  as  other  groups  of  animals,  to  the  best 
account,  and  thus  make  the  lower  forms  of  animal  life 
serve  man,  who  is  deservedly  at  the  head  of  creation  so 
long  as  he  shows  his  fitness  to  rule. 

ORDERS   OF   INSECTS. 

Thysanura  —  Springtails.  Neuroptera  —  Ant  Lions. 

Odonata  —  Dragon  Flies.  Lepidoptera  —  Butterflies. 

Orthoptera  —  Locusts.  Diptera  —  Flies. 

Hemiptera  —  Bugs .  Coleoptera  —  Beetles. 

Hymenoptera  —  Bees. 


CHAPTER    III. 
BRANCH   ARTHROPODA. 

CLASS    MYRIAPODA. 

Myriapoda.  —  The  myriapods  (" thousand  legs"  and  cen- 
tipeds)  have  a  wormlike  form,  but,  like  other  Arthropods, 
have  a  more  or  less  hardened  external  skeleton,  and  possess 
jointed  appendages.  The  head  is  distinct,  but  after  it  the 
segments  are  alike,  there  being  no  distinction  of  thorax 
and  abdomen.  On  the  sides  or  ventral  surface  of  most  of 
the  segments  are  the  spiracles  or  breathing  pores,  which 
lead  to  the  air  tubes,  or  tracheae,  as  in  the  insects. 


FIG.  38.    CENTIPED. 

The  head,  as  in  insects,  appears  to  be  composed  of  sev- 
eral segments,  fused  together ;  it  bears  a  pair  of  many- 
jointed  antennae,  a  pair  of  eyes,  and  two  or  three  pairs 
of  jaws. 

There  are  two  principal  groups,  the  centipeds  and  the 
millipeds.  The  centipeds  have  flattened  bodies,  with  one 
pair  of  legs  to  each  segment.  They  are  carnivorous,  and 
have  a  poison  gland  opening  at  the  tips  of  the  first  pair  of 
legs,  which  act  with  the  mouth  parts.  The  millipeds,  or 
thousand  legs,  have  cylindrical  bodies,  and  may  be  recog- 

54 


Myriapoda.  55 

nized  by  their  habit  of  coiling  into  a  spiral  when  disturbed  ; 
they  have  two  pairs  of  legs  to  each  segment.  They  are 
vegetarian  and  not  poisonous. 


FIG.  39.    SKEIN  CENTIPED. 

Both  of  these  forms  are  usually  to  be  found  by  over- 
turning stones  and  logs ;  the  centipeds  seek  safety  by  run- 
ning briskly  away,  while  the  millipeds  coil  up  and  lie  still. 

CLASS   ARACHNIDA. 

The  Spiders.  —  The  body  of  a  spider  consists  of  two 
parts,  connected  by  a  constricted  waist,  the  unsegmented 
cephalothorax  and  ^,  large,  soft,  unsegmented  abdomen. 
There  are  six  pairs  of  appendages  :  first,  the  jaws,  each 
jaw  ending  in  a  sharp,  incurved  segment  at  whose  apex 
opens  the  duct  of  a  poison  gland ;  second,  the  palps,  which 
are  sometimes  mistaken  for  a  pair  of  legs ;  and  lastly,  four 
pairs  of  legs. 

Spiders  have  from  one  to  four  pairs  of  simple  eyes  vari- 
ously arranged  on  the  top  or  front  of  the  head.  Spi- 
ders have  a  well-developed  sense  of  sight,  and  their  sense 
of  touch  is  very  delicate.  Of  their  other  senses  little  is 
known. 


Descriptive  Zoology. 


FIG.  40.    JUMPING 
SPIDER. 


They  suck  the  blood  of  insects,  which  they  kill  by  means 
of  the  poison  introduced  through  the  biting  jaws.  Their 
bite  is  seldom  serious  to  man,  though  one  of  the  larger 
spiders  is  said  to  kill  small  birds.  There 
is  a  strong  sucking  stomach  which  is 
worked  by  special  muscles. 

In  addition  to  breathing  by  air  tubes, 
as  in  the  case  of  insects,  spiders  also  have 
what  are  called  lungs,  or,  from  their 
peculiar  structure,  "lung  books."  The 
openings  to  these  lungs  are  under  the 
abdomen.  The  cavity  to  which  the 
opening  leads  is  somewhat  like  the  inside 
of  a  pocketbook,  with  a  number  of  com- 
partments. Blood  flows  around  the  out- 
side of  this  lung  book,  and  within  the 
plates  or  leaves  of  the  "book."  Thus  the  blood  and  the 
air  come  near  each  other,  separated  only  by  a  thin  mem- 
brane, and  by  the  folding  an  increase  of  surface  is  secured. 
This  is  the  same  general  plan  of  all  lungs  and  gills,  but 
the  details  of  the  plan  are  carried  out  in  various  ways. 

Like  crustaceans,  spiders  molt,  and  one  may  often  find 
their  cast  skins,  looking  like  dead  spiders,  but  closer  exami- 
nation will  reveal  the  difference. 

Spinning.  —  One  of  the  most  interesting  of  the  habits  of 
spiders  is  their  web  making.  There  is  a  great  difference 
among  spiders  in  this  regard.  Some  spiders  spin  very 
little,  leading  a  wandering  life.  Among  these  are  tne 
"jumping  spiders,"  so  named  from  their  habit  of  creeping 
stealthily  close  to  their  victims,  and  then  suddenly  pounc- 
ing upon  them.  These  forms  are  common,  and  their 
habits  are  exceedingly  interesting.  But  probably  most 
people  are  rather  more  familiar  with  the  spiders  that  make 


Arachnida. 


57 


the  conspicuous  webs.  These  kinds  lead  a  rather  seden- 
tary life,  preferring  to  set  traps  for  their  game  rather  than 
actively  hunt  for  it. 

The  spinning  apparatus  consists  externally  of  two  or 
three  pairs  of  short  segmented  appendages  under  the  tip 
of  the  abdomen.  Each  of  these  spinnerets  has  many  short, 
hairlike  projections,  with  a  perforation  at  the  tip  of  each. 


FIG.  41.    THE  SPINNERETS  OF  THE  COMMON  GARDEN  SPIDER. 

Within  the  abdomen  are  glands  which  secrete  a  liquid  sub- 
stance of  which  the  web  is  made.  When  the  spider  wishes 
to  spin  it  presses  the  spinnerets  against  some  surface,  and 
the  exuded  liquid  adheres ;  then  as  the  liquid  is  drawn  out 
into  a  slender  thread  it  hardens  as  it  is  drawn,  making  a 
thread  often  of  hundreds  of  strands  united.  The  feet  of 
the  spiders  have  blunt  claws  with  a  series  of  teeth,  by 
means  of  which  they  can  easily  walk  on  the  web  without 
tearing  it.  In  spinning  the  webs  with  radiating  and  concen- 
tric lines,  such  as  we  have  often  noticed,  the  spider  first 
spins  a  few  foundation  threads,  then  the  radiating  threads. 


58  Descriptive  Zoology. 

After  this  it  begins  at  the  •  center  and  proceeds  spirally 
outward ;  but  when  this  spiral  web  is  completed  it  begins 
once  more  at  the  outside,  and  takes  up  this  spiral  and 
replaces  it  with  a  spiral  spun  in  the  reverse  direction.  It 
bites  off  the  first  spiral,  and,  rolling  it  up  into  little  balls, 
drops  them  to  the  ground,  hence  it  was  formerly  supposed 
to  eat  the  web.  The  web  is  not  placed  quite  vertically, 


FIG.  42.    HEAD  AND  MANDIBLES  OF  COMMON  GARDEN  SPIDER. 

The  spots  above  are  eyes. 

and  the  spider  hangs  on  the  under  side,  so  that  when  a  fly 
is  caught  it  can  run  to  a  point  over  it  and  drop  down  and 
quickly  catch  it.  It  is  usually  the  female  that  is  on  the 
web,  while  the  male  may  be  hidden  near  by.  The  male  is 
sometimes  much  smaller  than  the  female  and  generally 
brighter-colored. 

We  have  often  wondered  how  it  is  that  on  some  bright, 
warm  summer  days  there  is  so  much  spider  web,  or 
"  gossamer,"  floating  in  the  air.  This  is  mostly  formed  by 
small  spiders.  They  climb  up  on  a  fence  or  stump,  or 
other  place  where  there  is  an  up  current  of  air,  caused  by 
the  heat  of  the  sun.  Standing  with  the  tip  of  the  abdomen 
pointing  upward  a  thread  is  started ;  the  current  carries  it 
upward  as  it  is  formed,  and  after  awhile  the  current  bears 
up,  not  only  the  thread,  but  the  thread  maker,  — the  spider 
itself,  —  and  they  may  often  be  seen  by  the  hundreds  float- 
ing along,  so  many  tiny,  unpatented  airships. 


Arachnida.  59 

It  is  said  that  these  gossamer  webs  are  a  sign  of  fair 
weather ;  so  these  little  creatures  seem  to  have  forerun 
mankind  in  forecasting  the  weather  as  well  as  in  aerial 
navigation. 

Some  spiders  construct  funnel-shaped  webs,  and  remain 
concealed  at  the  small  end  of  the  funnel,  ready  to  rush  out 
when  their  delicate  sense  of  touch  informs  them  that  some- 
thing is  shaking  the  web,  as  when  an  insect  is  caught. 
Gently  disturb  such  a  web,  and  see  the  occupant  dart  forth. 

Another  use  of  the  web,  and  almost  the  only  use  in  some 
spiders,  is  as  an  envelope  for  the  eggs.  The  web  forms  a 
silky  but  tough  covering,  usually  deposited  in  some  place 
of  safe-keeping,  but  rarely  carried  by  the  mother.  There 


FIG.  43.    SPIDER,  WITH  COCOON  ATTACHED  TO  SPINNERETS. 

are  many  eggs  in  one  such  case,  and  when  hatched 
the  little  spiders  sometimes  become  cannibals,  each  eating 
as  many  as  it  can  of  its  brothers  and  sisters. 

Kinds  of  Spiders.  —  There  are  many  kinds  of  spiders ; 
among  the  largest  is  the  tarantula ;  the  bite  of  this  and  of 
some  other  large  spiders  is  very  painful  to  man,  but  most 
of  the  stones  told  of  spider  bites  are  gross  exaggerations. 
The  trapdoor  spider  is  an  interesting  form  ;  it  lives  in  a 
hole  in  the  ground,  lines  its  hole  with  web,  and  makes  a 
lid  which  it  hinges  with  the  web.  One  spider  lives  under 
water,  forming  an  arched  web,  under  which  it  stays,  carry- 
ing down  bubbles  of  air  which  are  introduced  beneath 
the  web. 


60  Descriptive  Zoology. 

Scorpions.  —  Scorpions  are  found  in  warm  countries, 
reaching  their  greatest  size  in  tropical  America  and  Africa. 
The  form  shown  in  Fig.  44  occurs  from  North  Carolina  to 
Florida.  Other  species  are  found  in  the  southwestern 
United  States  as  far  north  as  Kansas.  The  body  consists 
of  a  short,  unsegmented  cephalothorax,  followed  by  a 
twelve-segmented  abdomen.  The  anterior  part  of  the  ab- 
domen is  broad,  the  hinder  part  narrow,  ending  in  the  poi- 


FIG.  44.   SCORPION. 

son  sting.  The  sting  is  painful  and  serious  to  man,  but 
seldom  fatal.  The  scorpions  are  nocturnal,  and  feed  on 
the  blood  of  insects.  Respiration  in  the  scorpions  is  by 
means  of  lung  books,  as  in  the  spiders. 

Harvestmen.  —  The  harvestmen,  or  daddy  longlegs,  are 
similar  to  spiders,  but  with  extremely  long  legs.  They 
frequent  shady  places,  and  live  chiefly  on  small  insects, 
such  as  plant  lice. 

Mites  and  Ticks.  —  These  are  small  and  often  degenerate 
forms  of  Arachnids.  Many  of  them  are  parasites,  sucking 
the  blood  of  mammals,  as  ticks  on  dogs,  cattle,  and  even 
man.  Among  the  mites  is  the  "itch  mite,"  which  has 
been  made  rare  by  the  spread  of  "soap  and  civilization." 


CHAPTER    IV. 
BRANCH   ARTHROPODA. 

CLASS   CRUSTACEA. 
Example  —  The  Crayfish. 

Occurrence.  —  Crayfishes  are  found  fairly  abundant  in 
streams  and  ponds  in  many  parts  of  the  United  States. 
They  may  be  seen  crawling  about  on  the  muddy  bottom, 
but,  being  nocturnal  in  their  habits,  they  usually  escape 
observation  during  the  daytime  by  hiding  in  holes,  under 
stones,  and  especially  under  ledges  of  rocks,  overhanging 
banks,  or  where  the  stream  has  washed  out  the  soil  about 
the  roots  of  trees  standing  on  the  banks. 

Crayfish  Holes.  —  Crayfishes  are  also  found  in  holes 
which  they  dig,  usually  in  low  ground.  When  the  water 
dries  up  from  the  ponds  and  creeks,  crayfishes  often  dig 
down  to  water,  and,  at  this  season,  live  in  these  holes. 
The  holes  are  frequently  many  feet  deep.  The  soil  and 
clay  are  brought  up  in  pellets,  and  with  these  a  "chimney" 
is  built  up  around  the  mouth  of  the  hole. 

How  the  Crayfish  Walks.  —  The  crayfish  walks  by  means 
of  the  last  four  pairs  of  thoracic  legs.  Each  of  these  legs 
has  seven  segments ;  and  the  successive  joints  admit  of 
motions  in  different  planes,  so  that  the  whole  appendage 
has  great  freedom  and  variety  of  movement.  The  cray- 
fish usually  walks  slowly,  holding  out  the  big  pinchers  in 
front.  It  can,  however,  walk  sideways  or  backward.  When 
taken  ^out  of  water  the  crayfish  walks  with  a  heavy,  awk- 

61 


62  Descriptive  Zoology. 

ward  movement,  frequently  bumping  its  body  upon  the 
floor ;  it  evidently  needs  the  buoyancy  of  the  water  to  sup- 
port its  weight. 

How  the  Crayfish  Swims.  —  Swimming  is  the  most  rapid 
action  of  the  crayfish,  and  it  probably  seldom  resorts  to  this 
means  of  locomotion  except  to  escape  enemies.  The  side 
parts  of  the  "  tail  fin  "  are  spread  out  as  wide  as  possible, 
and  the  whole  abdomen  is  suddenly  and  forcibly  bent  down, 
under,  and  forward.  This  makes  a  powerful  stroke,  and 
drives  (or  rather  pulls)  the  crayfish  swiftly  backward.  The 
whole  of  the  under  surface  of  the  abdomen  is  concave,  thus 
getting  a  good  hold  on  the  water.  As  the  animal  darts 
backward  the  resistance  is  greatly  reduced  by  the  convexity 
and  smoothness  of  the  dorsal  surface  of  the  abdomen. 
Again,  since  the  big  pinchers  rather  necessarily  extend 
forward,  it  would  be  difficult  for  the  crayfish  to  move  for- 
ward with  any  considerable  speed ;  but  when  it  darts  back- 
ward the  big  claws  drag  along  in  the  wake  without  any 
special  resistance.  It  should  be  further  observed  that  when 
the  crayfish  is  frightened,  the  chances  are  that  it  is  on  or 
near  the  bottom,  which  in  most  cases  is  more  or  less  muddy  ; 
when  the  powerful  tail  ^stroke  is  made,  it  would  naturally 
sweep  close  to,  if  not  actually  touch,  the  muddy  bottom. 
This  stirs  up  the  mud,  and  thus  makes  the  water  turbid 
between  the  pursuer  and  the  pursued,  and  greatly  favors 
the  chances  of  escape. 

The  Muscles  of  Locomotion.  —  The  muscles  which  move 
the  appendages  are  inclosed  in  the  framework  along  the 
ventral  surface  of  the  cephalothorax.  The  muscles  which 
flex  and  extend  the  abdomen  in  the  act  of  swimming  fill 
most  of  the  space  in  the  abdomen.  As  would  be  expected, 
the  extensor  muscles  are  much  smaller  than  the  flexors. 
The  extensors  arise  from  the  side  walls  of  the  thorax,  and 


FIG.  45.    EXTERNAL  FEATURES  OF  THE  LOBSTER. 

From  Packard's  Zoology. 


64 


Descriptive  Zoology. 


extend  back  into  the  abdomen,  being  attached  to  the  an- 
terior edges  of  the  abdominal  rings  in  the  upper  part  of  the 
abdomen.  When  these  muscles  shorten  they  pull  the  an- 
terior edge  of  each  tergum  under  the  posterior  edge  of  the 
preceding  tergum,  and  thus  straighten  the  abdomen.  The 
extensor  muscles  lie  above  the  intestine.  Below  the  intes- 
tine, and  filling  out  most  of  the  space  of  the  abdomen,  are 
the  flexor  muscles.  These  are  very  complicated.  Like  the 


Extensor  muscle. 


Abdominal  artery. 

Tergum. 


Intestine. 


Flexor  muscles. 


Epimerum.        Ventral         l^t  W//      \  Pleurum. 

abdominal  artery.      ^1^  Tpf  Nerve  cord. 

Sternum. 
19,  one  of  the  swimmerets. 

FIG.  46.    CROSS  SECTION  OF  ABDOMEN  OF  CRAYFISH. 

From  Huxley's  Crayfish. 

extensor  muscles,  they  originate  in  the  thorax,  and  extend 
back  and  are  inserted  on  the  sternums ;  and  when  they 
shorten,  they  flex  the  abdomen,  giving  the  powerful  stroke 
by  which  the  animal  swims  backward  so  rapidly. 

Food  of  the  Crayfish,  and  Mode  of  Eating.  —The  crayfish 
lives  largely  on  worms,  the  larvae  of  insects,  with  which 
most  waters  abound,  snails,  etc.  The  crayfish  is  carnivorous 
by  choice,  yet  by  necessity  may  be  almost  omnivorous.  It 
is  a  greedy  eater,  and  does  not  disdain  carrion.  It  is  de« 


Crustacea. 


cidedly  useful  as  a  scavenger,  disposing  of  a 
great  amount  of  dead  and  decaying  material 
which   would   polluce   the   water,          ^ 
such  as  dead  fish,  clams,  etc.     In 
eating,    the    big     pinchers    may 
tear   the    food    to    pieces, 
and  then  the  smaller  pinch- 
ers of  the  second  and  third 
pairs  of  legs  may  transfer 
the  pieces  to  the  mouth,  the 
entrance  to  which   is   sur- 
rounded by  the  maxillipeds. 
Or,  instead  of  this  process, 
the  crayfish  may  apply  the 
mouth  directly  to  the  food, 
and  gnaw  it  off  in  bits  by 
means  of  the  mandibles  and 
maxillipeds.     Crayfishes 
are    frequently    guilty    of 
cannibalism. 

The  Digestive  System  of 
the  Crayfish.  —  The  mouth 
of  the  crayfish  is    on    the 
under  surface  instead  of  at      f 
the  front  of  the  head,   as 
in  many  animals.     There 
are    six   pairs  of    mouth    parts,  —  the 
mandibles,  two  pairs  of  maxillae,  and 
three    pairs    of    maxillipeds.      These 
jaws  all  move  sidewise  ;  and  when  all  of  them 
are  closed,   the    third    or   hindmost   pair   of 
maxillipeds  cover  all  the  others.     The  short 
gUlet  passes  straight  up  from  the  mouth  to 


66  Descriptive  Zoology. 

the  stomach,  which  is  situated  in  the  head.  The  stomach 
is  very  complicated.  It  has  in  its  walls  a  set  of  arms  or 
levers  so  jointed  together  as  to  support  the  walls  of  the 
stomach.  Further,  these  bars,  which  are  composed  of 
chitin,  are  acted  on  by  sets  of  muscles  on  the  outside. 

There  are  teeth  on  the  inner  walls  of  the  stomach,  some 
projecting  inward  from  each  side  and  some  from  the  upper 
surface.  Certain  muscles  attached  to  the  outside  of  the 
stomach  act  in  such  a  manner  as  to  make  these  teeth  work 
together  and  masticate  food  in  the  stomach.  The  function 
of  the  stomach  is  wholly  masticatory,  and  it  has  no  digestive 
function.  At  the  hinder  part  of  the  stomach  there  is  a 
series  of  stiff  hairs  which  act  as  a  strainer,  so' that  only 
very  fine  particles  are  allowed  to  pass  on  into  the  intestine. 
Alongside  the  stomach  on  each  side  is  the  large  digestive 
gland.  Each  of  these  opens  by  a  duct  into  the  intestine  just 
back  of  the  stomach.  These  glands  were  formerly  called 
livers,  but  in  function  they  more  closely  resemble  a  pancreas, 
their  secretion  digesting  proteids  and  fats,  and  perhaps 
also  starches.  Beyond  the  stomach  the  intestine  extends 
in  a  nearly  straight  course  along  the  upper  part  of  the 
abdomen,  ending  in  the  anus  on  the  under  surface  of  the 
telson. 

Respiration  in  the  Crayfish.  —  The  crayfish  breathes  by 
means  of  the  plumelike  gills,  which  are  covered  by  the 
sides  of  the  carapace.  Each  gill  has  two  blood  tubes  in  its 
stem,  through  one  of  which  the  blood  enters,  while  it  returns 
through  the  other  tube.  In  the  feathery  branches  of  the 
gill  the  blood  is  separated  from  the  water  by  merely  a 
thin  membrane,  so  that  the  blood  and  the  water  make  an 
exchange,  the  blood  getting  oxygen  from  the  water,  and 
giving  to  the  water  the  waste  products  —  such  as  carbon 
dioxid  —  which  it  contains. 


Crustacea.  67 

There  are  Two  Sets  of  Gills.  —  One  row  is  attached  to 
the  bases  of  the  thoracic  appendages ;  these  are  the  foot 
gills.  A  second  row  arises  from  the  joints  by  which  the 


FIG.  48.    CROSS  SECTION  OF  A  CRAYFISH  THROUGH  THE  HEART. 

Showing  the  gills,  blood  currents,  and  water  currents. 

thoracic    appendages   are   attached   to  the  thorax;    these 
are  the  joint  gills.     (In  the  lobster  there  is  a  third  set, 


68  Descriptive  Zoology. 

higher  still,  arising  from  the  side  of  the  thorax,  and  called 
the  wall  gills.)  The  lowest  set,  the  foot  gills,  have  leaflike 
extensions  along  their  borders,  which  perhaps  serve  to  keep 
the  filaments  of  the  gills  from  becoming  entangled  with 
one  another.  The  gills  all  have  their  free  ends  extending 
upward.  The  direction  in  which  the  gills  extend  is  in 
keeping  with  the  fact  that  the  water  which  bathes  the  gills 
enters  about  the  bases  of  the  legs,  and,  passing  over  the 
gills,  escapes  near  the  anterior  end  of  the  cephalothorax, 
back  of  the  base  of  the  antenna  of  each  side.  It  has  been 
observed  that  the  cephalic  groove  marks  the  distinction 
between  the  head  and  the  thorax.  This  groove  also  marks 
the  anterior  limits  of  each  gill  chamber.  In  the  extreme 
anterior  part  of  the  gill  chamber,  extending  obliquely  up- 
ward and  backward,  is  the  gill  paddle  or  gill  scoop.  It  is 
a  part  of  the  second  maxilla.  It  is  attached  by  its  middle 
part,  and  each  end  is  a  somewhat  spoon-shaped  paddle. 
By  a  constant  back-and-forth  motion  this  paddle  continu- 
ally bails  the  water  out  at  the  anterior  end  of  the  gill 
chamber,  and  thus  draws  more  water  in  at  the  lower  border 
of  the  gill  cover,  between  the  bases  of  the  thoracic  legs. 

Circulation  in  the  Crayfish.  —  The  heart  is  situated  in 
the  dorsal  part  of  the  cephalothorax.  From  its  anterior 
end  arise  five  arteries :  a  single  artery  in  the  middle  line 
supplies  the  eyes ;  back  of  this  a  pair  run  to  the  antennae ; 
and,  still  further  back,  a  pair  lead  to  the  digestive  glands 
of  the  two  sides.  At  the  posterior  end  of  the  heart  arises 
one  artery,  which  almost  immediately  divides  into  two 
branches;  the  first  branch  runs  straight  back,  just  above 
the  intestine,  and  is  called  the  dorsal  abdominal  artery; 
the  other  branch  extends  downward,  passing  through  the 
nerve  cord.  After  passing  through  the  nerve  cord  it  again 
divides  into  two  branches,  one  running  forward,  the  sternal 


Crustacea.  69 

artery,  and  the  other  extending  backward,  the  ventral  ab- 
dominal artery. 

All  these  arteries  divide  and  subdivide,  forming  capil- 
laries. But  the  capillaries  do  not  reunite,  forming  veins; 
they  empty  into  more  or  less  irregular  spaces  in  the  body, 
around  the  muscles  and  other  internal  organs.  All  these 
spaces,  or  sinuses,  as  they  are  called,  lead  into  one  main 
channel,  the  sternal  sinus,  which  extends  along  the  middle 
of  the  ventral  region.  From  this  sinus,  passageways  con- 
duct the  blood  to  each  gill.  In  each  gill  one  tube,  the 
afferent  vein,  conveys  the  blood  to  the  gill  filaments ;  while 
another  tube,  the  efferent  vein,  returns  the  blood  to  another 
set  of  veins,  called  the  branchio-cardiac  veins,  which  lead 
to  the  pericardium.  There  are  no  tubes  to  convey  the 
blood  into  the  heart,  but  the  blood  enters  the  heart  directly 
through  three  pairs  of  holes,  one  on  each  side,  a  pair  on  top, 
and  another  pair  below.  These  holes  have  lips  on  the 
inside,  which  act  as  valves,  allowing  the  blood  to  enter 
freely,  but  preventing  a  reflow  through  the  holes.  Thus 
the  beating  of  the  heart  causes  a  constant  flow  of  blood  in 
one  direction :  first  to  the  tissues  of  the  body  in  general, 
where  it  gives  up  oxygen  and  food  materials  and  picks  up 
carbon  dioxid ;  then  to  the  gills,  where  it  gives  off  carbon 
dioxid  and  gains  oxygen ;  then  back  again  to  the  heart. 
The  blood  is  colorless,  but  after  exposure  to  the  air  it 
turns  bluish. 

Excretion  in  the  Crayfish.  —  In  connection  with  the  study 
of  the  gills  we  have  seen  how  the  carbon  dioxid  is  removed 
from  the  body.  But  the  nitrogenous  wastes  are  excreted 
by  a  pair  of  kidneys,  which  are  called,  on  account  of  their 
color,  the  green  glands.  They  are  situated  in  the  head, 
just  below  and  in  front  of  the  stomach.  The  gland  proper 
is  a  button-shaped  body,  lying  close  to  the  ventral  body 


yo  Descriptive  Zoology. 

wall.  This  leads  into  a  thin  sac,  which  serves  as  a  bladder, 
and  it  in  turn  opens  by  a  duct  to  the  exterior,  through  the 
apex  of  a  hard,  white,  conical  papilla,  on  the  ventral  surface 
of  the  base  of  each  antenna. 

It  is  worthy  of  notice  that  the  current  of  water  coming 
from  the  gills  passes  directly  by  this  other  exit  of  waste, 
so  that  one  stream  carries  away  all  the  waste  products, 
avoiding  duplication  of  machinery. 

The  Nervous  System  of  the  Crayfish.  —  The  nervous  sys- 
tem consists  of  a  nerve  cord  which  lies  on  the  floor  of  the 
body  cavity,  extending  the  whole  length  of  the  body  in  the 
middle  line.  It  is  a  white  cord,  composed  of  a  ganglion 
for  each  segment,  connected  in  line  by  nerve  fibers.  The 
cord  is  really  double,  but  the  two  rows  of  ganglions  have 
consolidated,  so  that  there  appears  to  be  but  one  row  of 
ganglions.  The  cord  itself,  between  the  successive  gan- 
glions, while  apparently  single,  is  actually  double.  And  in 
two  places  the  double  nature  of  the  cord  is  manifest.  The 
two  parts  of  the  cord  pass  on  the  right  and  left  of  the 
gullet,  forming  what  is  called  the  esophageal  ring,  or 
esophageal  collar  ;  again,  the  sternal  artery  passes  between 
the  two  halves  in  the  interval  between  two  of  the  gan- 
glions. Though  there  is  a  ganglion  for  each  segment, 
there  is  a  consolidation,  so  that  there  are  but  thirteen  dis- 
tinct ganglions  for  the  twenty  (or  twenty-one)  segments. 
The  first  ganglion,  called  the  brain  or  the  cerebral  ganglion, 
is  the  result  of  the  fusion  of  three  pairs  of  ganglions.  Back 
of  the  gullet,  and  connected  to  the  brain  by  the  two  com- 
missures passing  on  either  side  of  the  gullet,  is  a  large 
ganglion,  which  is  evidently  composed  of  the  ganglions  of 
the  last  three  cephalic  segments  united  with  the  ganglions 
of  the  first  three  segments  of  the  thorax.  Following  this 
are  five  more  distinct  ganglions  in  the  thorax  and  six  in  the 


Crustacea. 


abdomen.  In  the  abdomen  the  nerve  cord  is  in  plain  view 
when  the  abdominal  muscles  have  been  removed.  But  in 
the  thorax  the  cord  is  concealed  in  a  groove  made  by  the 


Antennule 
nerve 


Antenna 
nerve 


Nerve  ring 
around  gullet 


Sternal  artery 


Ganglion  7 


Anus 


FIG.  49.    NERVOUS  SYSTEM  OF  CRAYFISH. 

From  Huxley's  Crayfish. 

inward  projecting  framework  which  supports  the  muscles 
which  move  the  appendages.  From  each  ganglion  nerves 
radiate  to  supply  the  adjacent  muscles  and  sense  organs. 


72  Descriptive  Zoology. 

The  Senses  of  the  Crayfish.  —  The  crayfish  appears  to 
have  the  senses  of  touch,  sight,  taste,  and  smell. 

The  Sense  of  Sight  —  The  eyes  are  on  movable  stalks. 
The  advantage  of  being  able  to  project  the  eyes  is  ap- 
parent. The  protection  afforded  by  withdrawing  the  eyes 
is  almost  equally  apparent  when  we  consider  that  cray- 
fishes fight  fiercely  with  each  other,  besides  being  frequently 
under  the  necessity  of  protecting  themselves  from  enemies 
outside  of  their  own  race.  The  projecting  rostrum  and 
the  sharp  blade  of  the  lamina  of  the  antenna  need  no  ex- 
planation as  to  their  use.  The  eye  of  the  crayfish  is  a 
typical  compound  eye.  It  is  made  up  of  distinct  parts, 
each  of  which  is  called  a  facet,  or  cornea. 

The  Sense  of  Touch.  —  One  does  not  need  to  experiment 
long  with  crayfishes  to  be  sure  that  they  feel  as  well  as  see. 
The  general  surface  of  the  body  is  more  or  less  sensitive 
to  touch,  but  with  such  a  hard  covering  this  sense  can 
hardly  be  other  than  a  very  dull  sense  over  most  of  the  area. 
But  the  antennae  are  specially  adapted  for  this  sense,  and 
their  long,  slender,  tapering  form  and  jointed  structure 
render  them  convenient  to  apply  to  surrounding  objects. 

Smell  and  Taste.  —  Certain  hairs  of  the  external  branch 
of  the  smaller  antennas  are  believed  to  be  connected  with 
the  sense  of  smell. 

There  is  in  the  basal  joint  of  each  antennule  a  sac, 
formed  by  the  depression  of  its  outer  surface,  so  that  free 
communication  is  left  with  the  surrounding  water.  This 
was  long  supposed  to  be  an  organ  of  hearing,  but  is  now 
regarded  as  the  seat  of  the  sense  of  equilibrium. 

There  is  no  doubt  that  the  crayfish  discriminates  in 
choice  of  food,  and  we  have  good  reason  to  believe  that 
the  sense  of  taste  is  present. 


Crustacea.  73 

The  Enemies  of  the  Crayfish.  —  Various  carnivorous 
fishes,  such  as  black  bass,  eat  crayfishes,  hence  the  fisher- 
man also  becomes  an  enemy  of  the  crayfish  by  capturing 
it  for  bait.  Raccoons  are  very  fond  of  crayfishes.  Both 
of  these  animals  are  nocturnal  in  their  habits  ;  so  when  the 
crayfish  sets  out  in  the  evening  to  get  a  lunch,  the  raccoon 
lunches  on  the  luncher.  One  who  frequents  the  woods 
may  see  the  raccoon  tracks  along  the  creeks  where  it  has 
been  seeking  this  and  other  aquatic  animals  for  food. 
Muskrats  and  crows  are  also  among  the  more  important 
enemies  of  the  crayfish. 

How  the  Crayfish  escapes  its  Enemies.  —  In  the  first  place 
its  nocturnal  habits  keep  it  out  of  sight  of  some  enemies. 
Second,  its  color  is  in  close  harmony  with  its  surroundings, 
so  that  it  is  very  inconspicuous.  Dull  shades  of  green, 
brown,  and  red  are  the  prevailing  colors. 

Though  the  senses  of  the  crayfish  are  none  of  them  very 
acute,  they  plainly  are  useful  in  making  the  animal  aware 
of  the  approach  of  enemies.  Then  it  is  usually  near  the 
bottom,  where  there  are  many  places  of  refuge.  And  last, 
but  not  least,  this  creature  has  one  kind  of  locomotion  that 
is  speedy,  that  of  swimming.  The  hard  covering  may 
make  the  crayfishes  objectionable  as  food  to  many  animals 
that  otherwise  would  eat  them.  The  big  pinchers,  too, 
which  he  knows  so  well  how  to  use,  are  no  mean  defense 
against  his  lesser  foes.  And  further,  the  threatening  atti- 
tude which  the  crayfish  assumes  when  cornered,  may 
intimidate  some  would-be  assailants  who  do  not  like  the 
looks  of  the  bristling  claws,  and  fear  that  the  "  bite  will  be 
as  bad  as  the  bark." 

The  Eggs  of  the  Crayfish. —  The  eggs  are  extruded 
as  usual,  but  instead  of  being  left  in  some  place  of  de- 
posit, are  attached  to  the  mother  by  being  glued  to  the 


74  Descriptive  Zoology. 

swimmerets.  The  eggs  are  small  and  smooth,  reddish  or 
dark,  and  in  the  mass  suggest  the  appearance  of  a  berry ; 
hence  the  mass  of  eggs  is  called  the  "berry."  A  lobster 
with  the  eggs  attached  is  called  a  "  berry  lobster."  From 
the  eggs  hatch  the  little  crayfishes,  which  have  the  form  of 
the  adult.  These  little  fellows  have  incurved  hooks  on  the 
ends  of  their  claws,  by  means  of  which  they  take  fast  hold 
of  the  swimmerets  of  the  mother  and  remain  so  attached 
for  some  time. 

Rate  of  Growth  of  Crayfishes.  —  The  crayfish  is  about  a 
quarter  of  an  inch  long  when  hatched.  At  the  end  of  the 
first  year  it  is  about  an  inch  and  a  half  long.  After  the 
first  year  it  grows  more  slowly,  and  seldom  becomes  more 
than  five  or  six  inches  in  length. 

Molting.  —  Since  the  hard  parts  are  on  the  outside, 
such  creatures  would  soon  reach  a  limit  of  growth  unless 
some  special  provision  were  made.  This  is  provided  for 
by  the  shedding  of  the  entire  outer  hard  covering  at  stated 
periods.  The  hard  shell  splits  across  the  dorsal  surface 
at  the  junction  of  the  cephalothorax  and  abdomen.  The 
carapace  also  usually  splits  part  way  forward  from  the 
transverse  opening  above  mentioned.  By  severe  effort 
the  cephalothorax  and  its  appendages  are  first  extracted ; 
then  the  abdomen  is  pulled  out  of  its  hard  covering.  This 
is  a  critical  period  in  the  life  of  the  crayfish.  Sometimes 
the  big  pinchers  are  broken  off  in  the  effort  to  get  them 
out  of  the  old  case.  Crayfishes  sometimes  perish  in  the 
struggle  to  get  free  from  their  "hide-bound"  condition. 
And  for  some  time  after  molting  the  body  is  soft,  and 
hence  almost  defenseless.  At  this  time  the  animal  is  un- 
usually timid,  and  lives  in  hiding  till  its  skin  again  hardens 
by  the  addition  of  limy  matter.  After  shedding,  the  cray- 
fish is  doubly  helpless;  not  only  is  his  body  soft  and  easily 


Crustacea.  75 

injured,  but  his  claws,  being  soft,  are. useless  as  weapons  of 
defense.  In  molting,  the  hard  lining  of  the  stomach,  with 
the  stomach  teeth,  is  also  shed.  Crayfishes  molt  several 
times  the  first  year,  the  number  of  molts  gradually  decreas- 
ing till  in  adult  life  the  molt  probably  takes  place  but 
once  a  year. 

"Crab's  Eyes."  —  Previous  to  the  time  of  molting  there 
appear  on  the  sides  of  the  stomach  two  button-shaped 
bodies  of  limy  material.  In  molting  they  are  shed  into 
the  cavity  of  the  stomach,  together  with  the  lining  of  the 
stomach.  It  is  believed  that  they  break  up,  become  dis- 
solved, and  are  absorbed  and  then  deposited  as  stiffening 
matter  in  the  chitin,  which  makes  the  basis  of  the  envelop- 
ing crust. 

Restoration  of  Lost  Limbs. — Crayfishes  often  lose  their 
legs  while  fighting.  Sometimes  also  they  seem  to  drop 
them  or  throw  them  off  when  badly  frightened,  but 
perhaps  they  are  merely  snapped  off  in  the  violent  effort 
to  escape.  The  legs  seem  to  break  off  always  at  the  same 
place,  where  the  leg  is  most  narrow,  and  this  is  the  easiest 
place  to  heal.  The  blood  quickly  coagulates,  and  such 
loss  seems  not  to  be  dangerous  or  even  serious.  The 
mutilated  stump  at  once  begins  to  grow  a  new  leg,  but 
for  a  long  time  it  is  smaller  than  its  mate.  If  one  looks 
over  a  number  of  crayfishes,  he  is  pretty  sure  to  find  some 
in  this  condition.  The  big  fighting  limbs  are  ordinarily 
the  ones  that  have  been  lost. 

Are  Crayfishes  Beneficial  or  Injurious  to  Man  ?  —  Crayfishes  are  good 
to  eat,  the  only  part,  of  course,  being  the  muscle,  most  of  which  is  in 
the  abdomen.  They  are  used  as  food  to  a  considerable  extent  in 
Europe,  but  they  are  little  used  in  this  country.  Crayfishes  are  very 
useful  as  scavengers,  eating  dead  fish,  etc.  Crayfishes  are  said  to 
benefit  some  heavy,  clayey  land  by  the  holes  they  dig,  perhaps  by  mak- 
ing the  soil  more  porous  and  helping  to  drain  it. 


76  Descriptive  Zoology. 

On  the  other  hand,  crayfishes  often  do  very  great  damage  by  digging 
holes  in  the  dikes  and  levees  along  the  lower  Mississippi.  These  holes 
gradually  become  enlarged,  perhaps  by  muskrats,  and  may  finally  cause 
the  levee  to  give  way,  inundating  vast  tracts  of  land  which  are  protected 
by  the  dikes-,  and  causing  immense  loss  of  property  and  sometimes  of 
life. 

Distribution  of  Crayfishes.  —  Crayfishes  are  fairly  common  through- 
out the  United  States,  more  especially  in  the  central  and  southern  por- 
tions. They  are  usually  more  abundant  in  regions  where  there  is  plenty 
of  limestone,  and  are  less  abundant  where  granite  rock  prevails,  as  in 
New  England.  They  are  to  be  found  in  Ireland  and  England  and  on 
most  of  the  continent  of  Europe,  in  Australia,  New  Zealand,  Madagas- 
car, and  Japan.  But  they  occur  in  very  limited  areas  in  Asia  and  South 
America.  In  Africa  none  have  ever  been  found. 

Origin  of  Crayfishes.  —  It  is  supposed  that  the  crayfishes  are  descend- 
ants of  marine  crustaceans  ;  that  some  of  these  forms  lived  about  the 
mouths  of  rivers,  gradually  became  accustomed  to  partly  freshened 
water,  and  in  time  to  fresh  water,  and  ascended  the  streams  and  entered 
lakes.  We  do  not  know  any  living  salt-water  crustacean  from  which 
the  crayfish  is  supposed  to  have  been  derived. 


CHAPTER   V. 
BRANCH  ARTHROPODA. 

CLASS  CRUSTACEA   (Continued}. 

Lobsters.  —  With  a  few  unimportant  exceptions,  the 
structure  of  the  lobster  is  essentially  the  same  as  that 
of  the  crayfish.  The  lobster  may  be  said  to  be  a  big  salt- 
water crayfish,  or  the  crayfish  a  small  fresh-water  lobster. 
Lobsters  are  an  important  food  product  of  the  North  At- 
lantic, both  to  the  old  world  and  the  new.  From  twenty 
to  thirty  millions  are  caught  annually  along  the  coasts  of 
New  England  and  Canada.  They  are  captured  by  sinking 
large  wooden  traps,  which  are  called  "  lobster  pots."  These 
are  baited  with  refuse  fish.  A  buoy  is  attached  to  each 
trap  to  mark  its  place,  and  to  serve  as  a  means  of  taking  up 
the  trap.  The  lobsters  thus  caught  average  less  than  four 
pounds  in  weight,  but  specimens  have  been  found  that 
weighed  as  high  as  thirty-nine  pounds. 

Shrimps  and  Prawns.  —  Two  other  marine  crustaceans 
that  are  largely  used  as  food  are  the  shrimps  and  prawns. 
These  are  essentially  like  the  crayfish,  but  differing  from 
it  more  than  the  lobster.  They  are  caught  in  large  numbers, 
and  eaten  fresh  or  canned,  as  is  the  lobster.  Prawns  have 
a  permanent  hump  on  the  dorsal  surface  of  the  abdomen ; 
and  the  dorsal  surface  rises  as  a  sharp  ridge,  perhaps  to 
diminish  resistance,  and  thus  increase  its  speed  when  swim- 
ming. Most  of  our  so-called  shrimps,  out  of  which  the 
famous  salad  is  made,  are  really  prawns,  and  not  shrimps. 

77 


7 8  Descriptive  Zoology. 

Crabs.  —  Though  differing  considerably  in  appearance, 
crabs  have  the  same  essential  structure  as  crayfishes  and  lob- 
sters. The  cephalothorax  is  broad  instead  of  being  rela- 
tively long  and  narrow.  The  abdomen  is  kept  folded  under 
the  cephalothorax,  and  is  not  used  in  swimming,  almost  its 
only  use  being  to  protect  the  eggs  in  the  female.  As  in  the 
preceding  forms,  there  is  the  hard  protecting  crust ;  stalked 
eyes;  several  mouth  parts  ;  five  pairs  of  large  thoracic  ap- 
pendages, the  first  pair  armed  with  big  pinchers ;  gills  on 


FIG.  50.    SHRIMP. 

the  sides  under  cover  of  the  carapace  ;  and  the  same  general 
manner  of  life.  Crabs  are  great  scavengers  ;  and  if,  while 
at  the  seaside,  one  wishes  to  clean  a  skeleton,  if  he  puts  it 
into  a  box  guarded  by  slats,  with  spaces  just  wide  enough 
to  let  crabs  in,  they  will  do  the  rest.  Crabs  may  be  caught 
by  tying  a  piece  of  meat  to  a  string  and  letting  it  down  off 
almost  any  wharf  or  rock  into  the  water.  When  the  crab 
takes  hold  with  the  pinchers  he  will  usually  hold  on  till  he 
reaches  the  surface ;  and  while  he  may  be  lifted  out  on  the 
wharf  or  bank,  it  is  safer  to  use  a  net  when  he  is  brought 
to  the  surface.  Though  most  crabs  are  good  to  eat,  and 
many  kinds  are  so  used,  the  one  most  eaten  is  the  blue  crab 


Crustacea. 


79 


(Callinectes  kastatus),  often  called  the  "  edible  crab."  Just 
after  they  molt  they  are  esteemed  good,  cooked  whole, 
under  the  title  "  soft-shelled  crabs." 

Swimming  crabs,  such  as  the  blue  crab,  have  the  last  pair 
of  thoracic  legs  developed  as  paddles,  by  means  of  which 
they  swim  sideways  with  considerable  rapidity.  In  the 


Swimming  legs. 

FIG.  51.    LADY  CRAB,  NATURAL  SIZE. 

case  of  crabs  that  do  not  swim,  the  last  legs  are  not  flat- 
tened, but  end  in  a  point  like  the  other  legs.  The  little 
oyster  crab  is  often  found  in  an  oyster  stew  (Fig.  52). 

Development  of  the  Crab.  —  It  is  very  interesting  to  note 
that  the  crab,  when  first  hatched,  has  nearly  the  form  of 
the  crayfish,  with  an  extended  abdomen  and  a  relatively 
narrow  body,  but  that  gradually  the  cephalothorax  widens, 
and  the  abdomen  becomes  folded  under  the  body.  Crabs 


8o  Descriptive  Zoology. 

are  regarded  as  the  highest,  and  probably  the  latest,  of  the 
crustaceans.  While  the  development  of  the  individual  does 
not  recapitulate  the  development  of  the  race  quite  so  fully 
as  in  some  other  groups,  it  serves  very  well  to  illustrate  the 
general  law  that  the  development  of 
the  individuals  of  the  highest  group 
is  an  epitome  of  the  development  of 
the  group  as  a  whole;  and  often  is  a 
recapitulation  of  the  order  of  geo- 
logical succession. 
FIG.  52.  OYSTER  CRAB. 

Cephalization.  —  By  this  term  is  meant  the 

higher  development  of  the  head,  and  of  the  appendages  belonging  to  and 
immediately  surrounding  the  head.  In  the  lower  forms  of  crustaceans 
the  head  does  not  predominate  as  in  the  crabs.  The  diameter  is  ap- 
proximately the  same  from  one  end  to  the  other.  Even  in  the  crayfish, 
the  ganglion  at  the  anterior  end  is  very  little  larger  or  better  developed 
than  those  of  the  abdomen.  In  the  crabs  there  is  a  much  greater  con- 
centration of  the  ganglions  in  the  thoracic  region.  This  principle  will 
be  illustrated  in  other  groups  of  animals,  but  it  can  be  seen  here  that  the 
higher  in  the  scale,  the  greater  is  the  development  of  the  head  regions. 

The  Sand  Crab.  —  This  crab,  with  numerous  others,  lives  out  of 
the  water  considerable  of  the  time.  It  is  sandy  in  color,  and  lives 
out  on  the  beach.  It  seems  to  be  rather  keen  sighted,  and  runs  at 
a  lively  rate  when  pursued.  It  usually  attempts  to  escape,  and  often 
succeeds,  by  burying  itself  in  the  sand.  This  it  does  in  a  wonderfully 
short  time.  With  a  few  quick,  jerky  motions  of  its  legs  it  buries  itself, 
usually  leaving  only  the  tips  of  its  two  eyes  projecting  above  the  surface. 
It  is  practically  concealed,  —  so  much  so  that  one  who  has  pursued  it, 
unless  he  looks  closely,  may  lose  sight  of  it ;  but  the  crab  has  its  enemy 
in  sight  all  the  time.  Its  means  of  escape  is  ingenious,  and  the  color  is 
a  fine  example  of  protective  resemblance. 

The  Fiddler  Crab.  — This  little  crab,  about  two  inches  wide,  has  one 
big  and  one  small  pincher,  suggesting  the  fiddle  and  bow.  These  very 
interesting  little  fellows  are  sometimes  so  thick  on  the  shore,  along  the 
water  line,  that  they  crowd  each  other  for  crawling  room,  and  make  a 
very  noticeable  rustling  noise  as  they  elbow  each  other  while  retreating 
from  the  inquisitive  biped,  of  whose  motives  they  are  suspicious. 


Crustacea. 


81 


Blind  Crayfishes.  —  In  the  Mammoth  Cave,  and  some  other  caves, 
are  found  blind  crayfishes.  This  does  not  mean  that  in  all  cases  eyes 
are  completely  lacking,  —  in  fact,  in  most  cases  rudiments  of  eyes  are 
present,  but  useless.  How  long  these  animals  have  thus  lived  in  dark- 
ness we  do  not  know ;  but  we  find  that  an  organ  that  is  no  longer  used 
may  lose  its  function  and  even  dwindle  away.  We  here  see  illustrations 
of  the  general  law  that  disuse  leads  to  deterioration  in  both  structure 
and  function,  often  resulting  in  complete  uselessness,  and  perhaps  com- 
plete atrophy  as  well. 

Hermit  Crabs.  —  These  crabs  back  into  an  empty  univalve  shell,  which 
they  carry  around  with  them  for  protection.  The  abdomen,  and  all  the 


FIG.  53.    BLIND  CRAYFISH  OF  MAMMOTH  CAVE,  NATURAL  SIZE. 

parts  except  the  head  and  projecting  appendages,  become  soft,  and  de- 
pendent upon  a  continuance  of  such  protection.  When  the  crab  gets 
too  big  for  the  shell,  he  hunts  for  a  bigger  one.  It  is  said  that  these 
crabs  sometimes  fight  over  shells.  One  hermit  meeting  another  crab 
that  has  a  shell  that  he  thinks  would  fit  him  better  than  the  one  he  has, 
ejects  the  other  fellow,  perhaps  only  to  find  that  he  has  gotten  a  misfit 
after  all,  and  so  goes  back  to  his  old  shell,  a  wiser  if  not  a  better  crab. 
Barnaeles.  —  If  one  lies  down  on  the  edge  of  almost  any  stone  pier 
or  wharf  along  the  coast  and  looks  down  into  the  water,  he  may  see  a 


82 


Descriptive  Zoology. 


general  wavelike  motion  as  if  hundreds  of  hands,  with  feathery 
fingers,  were  constantly  opening  and  closing.  Looking  closer,  he  will 
see  that  these  feathers  are  in  clusters,  each  projecting  from  the  apex  of  a 
cone-shaped  body  whose  base  is  attached  to  the  rock  wall.  These  are 
acorn  barnacles.  Disturb  them  and  they  will  draw  in  their  feathery 
appendages  and  close  the  shelly  valves  that  guard  the  opening.  They 
resemble -bivalve  mollusks,  and  in  fact  were  regarded  as  mollusks  until 
it  was  discovered  that  when  young  they  are  like  the  young  of  the  lower 
Crustacea.  After  leading  a  free-swimming  life  for  a  time,  they  attach 


FIG.  54.    HERMIT  CRAB  IN  SHELL  OF  SEA  SNAIL. 

themselves  by  the  head  end  to  a  rock,  and  thenceforth  live  anchored  to 
this  one  spot.  They  have  given  up  locomotion,  and  become  sessile. 
The  law  of  progress  in  evolution  is  toward  greater  freedom,  as  illus- 
trated in  many  forms  of  animal  life ;  but  here  we  have  a  good  example 
of  retrograde  development,  or  degeneration.  Almost  the  only  ready 
indication  of  its  crustacean  relationship  is  the  segmentation  of  the 
appendages. 

Another  form  of  barnacle  is  the  goose  barnacle,  which  has  a  body 
resembling  a  clam,  attached  by  a  soft,  flexible  stalk  to  some  solid 
object,  frequently  to  a  piece  of  floating  timber.  When  actively  feeding, 
the  shell  opens  and  the  feather-like  feet  extend  in  lively  motion,  but 


Crustacea.  83 

they  are  withdrawn  and  shut  in  if  the  animal  is  disturbed.  In  its  devel- 
opment the  goose  barnacle  has  about  the  same  history  as  the  acorn 
barnacle. 

Other  Degenerate  Crustaceans.  —  Degenerate  as  are  the  barnacles, 
there  are  still  lower  crustaceans.  Various  crustaceans  have  become 
parasites,  living  attached  to  whales,  fishes,  etc.,  and  have  become  so 
degenerate  as  to  have  lost  all  likeness  to  the  typical  crustacean  struc- 
ture, so  that  no  one  would,  without  pro- 
longed investigation,  even  suspect  that  they 
belonged  to  this  group. 

All  of  the  above  cases,  blind  crayfish, 
hermit  crab,  barnacles,  and  parasitic  crus- 
tacea,  illustrate  one  general  principle,  that 
disuse  leads  to  atrophy,  and  that  parasitic 
habits  involve  degeneration  in  structure  as 
well  as  in  function. 

Classification  of  Crustacea.  —  The  crus- 
tacea  are  divided  into  two  subclasses,  the 
Entomostraca  and  the  Malacostraca. 

The  Entomostraca  are  of  comparatively  FlG"  55'  GooSE  BARNACLES- 
simple  structure,  usually  small,  sometimes  ^^Lgy^"^6 

microscopic.     The  number  of  segments  is 

variable,  and  the  appendages  are  very  similar  throughout.  We  may 
briefly  consider  some  of  the  leading  orders. 

Some  of  the  Phyllopoda  are  covered  by  a  flat,  shield-shaped  carapace ; 
others  have  a  bivalve  shell  which  does  not  inclose  the  head.  Some 
Phyllopods  have  no  carapace.  In  some  forms  the  body  is  unsegmented, 
and  there  are  leaflike,  lobed,  swimming  feet. 

The  Ostracoda  are  small  and  the  head  as  well  as  the  rest  of  the 
body  is  inclosed  in  a  bivalve  shell,  somewhat  resembling  a  little  clam. 

The  Copepoda  may  be  represented  by  the  cyclops,  or  water  flea. 
Fig.  56.  This  form  is  common  in  sluggish  streams  and  ditches.  It 
is  white,  large  enough  to  be  seen  by  the  naked  eye,  and  swims  by  a 
jerky  motion  of  the  antennae,  which  are  its  largest  and  strongest 
appendages.  The  female  bears  two  large  egg  masses. 

The  Cirripedia  comprise  the  barnacles  above  mentioned. 

The  Malacostraca  comprise  the  higher  Crustacea.  They  are  usually 
of  considerable  size,  and  the  number  of  segments  is  rather  constant, 
instead  of  variable  as  in  the  Entomostraca.  There  may  or  may  not  be 


Descriptive  Zoology. 


a  carapace,  and  the  head  may  consist  of  but  one  piece,  formed  by  the 
consolidation  of  several  segments  (usually  five).  The  thorax  has  eight 
segments  and  the  abdomen  usually  seven. 

Without  attempting  to  enumerate  the  orders,  we  may  mention  the 
Amphipoda,  and  illustrate  them  by  the  beach  fleas  and  sand  hoppers, 


FIG.  56.    WATER  FLEA  (CYCLOPS). 

Female  with  egg  sacs.     There  is  a  single  eye  with  two  facets. 

which  have  a  laterally  compressed  body,  the  anterior  legs  bearing  gills, 

and  the  posterior  used  for  jumping. 

The  Isopoda  have  a  body  flattened  from  above,  and  bear  gills  on  the 

abdominal  appendages,  as  in  the  sow  bug,  shown  in  Fig.  57. 

The  Drcapoda.  or  ten-footed  Crustacea,  are  so  named  from  the  five 

large  pairs  of  thoracic  appendages  observed  in  the  crayfish,  which  serves 
as  an  example  of  the  group.  The  Decapods 
are  somet^mes  further  divided  into  the 
Macrura,  or  long-tailed  forms,  such  as  the 
crayfish  and  lobster,  and  the  Brachyura,  or 
short-tailed  forms,  such  as  the  crabs. 


FIG.  57.    Sow  BUG 
(Crustacean). 


Characters  of  Crustacea.  —  i .  The 

crustaceans  have  a  hard  cuticle, 
formed  by  the  underlying  skin.  The  cuticle  consists 
largely  of  a  substance  called  chitin,  which  is  tough  and 
more  or  less  elastic.  The  chitin  becomes  more  or  less 
infiltrated  by  carbonate  of  lime,  and  is  thus  made  harder. 


Crustacea.  85 

2.  But  the  limy  material  is  not  deposited  everywhere  in 
the  cuticle.     Certain  places  are  left  for  joints.     At  these 
places  the  chitin  remains  flexible.     Hence  we  have  a  series 
of  segments  joined  together,  five  in  the  head,  consolidated, 
eight  in  the  thorax,  and  usually  seven  in  the  abdomen, 
twenty  being  the  typical  number  in  the  higher  forms. 

3.  Not  only  is  the  body  segmented,  but  normally  each 
segment  bears  a  pair  of  appendages,  which  are  themselves 
segmented.     The  eyes  are  no  longer  regarded  as  append- 
ages, but   outgrowths   of   the  head,  which    later   become 
movable  by  means  of  a  joint. 

4.  Most  crustaceans  have  gills  and  lead  an  aquatic  life. 
Some  of  the  simpler  forms  breathe  by  the  whole  surface 
of  the  body,  and  a  few  forms  which  have  gills  live  out  of 
water,  but  usually  in  damp  places.     The  gills  remain  moist, 
a  small  amount  of  water  serving  to  transmit  the  oxygen 
from  the  air  to  the  blood  within  the  gills. 

5.  Crustacea  normally  possess  two  pairs  of  antennae. 

6.  Most  crustaceans  have  compound  eyes. 

7.  Crustaceans    are    an    active    group,    but,    as    above 
noticed,  some  are  sessile,  and  others  parasitic. 

The  King  Crab.  —  The  king  crab,  or  horseshoe  crab,  has  a  body 
shaped  somewhat  like  a  horseshoe.  A  six-sided  abdomen  fits  into  a 
deep  notch  in  the  posterior  margin  of  the  cephalothorax,  and  ends  in  a 
long,  tapering  spine.  On  the  cephalothorax  is  one  pair  of  simple  and 
one  pair  of  compound  eyes.  The  mouth  is  in  the  center  of  the  under 
surface,  between  the  bases  of  the  legs,  and  a  series  of  leaflike  gills  are 
to  be  found  under  the  abdomen.  The  king  crab  is  found  along  our 
Atlantic  coast,  often  burrowing  in  the  sand.  It  molts  by  splitting  the 
shell  along  the  anterior  margin.  The  hard  crust,  the  molting,  the  gills, 
and  general  mode  of  life  would  seem  to  ally  the  king  crabs  to  the  Crus- 
tacea, but  later  researches  place  them  nearer  the  spiders.  They  have 
some  points  of  relationship  with  the  extinct  trilobites,  and  are  especially 
interesting  as  the  only  known  survivors  of  their  race. 


86 


Descriptive  Zoology. 


CHARACTERISTICS  OF  ARTHROPODS. 

1.  Arthropods  have  an  external  skeleton,  or  exoskeleton. 

2.  This  skeleton  consists  of  a  series  of  rings,  movable 
upon  one  another,  i.e.  the  skeleton  is  segmented. 

3.  Some  of  these  rings,  or  segments,  bear  appendages 
that  are  segmented. 

CLASSIFICATION  OF  ARTHROPODA. 


ARTHROPODA. 

Crustacea  (Class  I).                                  (Tracheata.) 

i.  Aquatic  (generally)  —  breathe             i.  Aerial  —  breathe  by  air  tubes 

by  gills. 

or  "  lungs." 

2.  Antennae  —  2  pairs.                                 2.  Antennas  —  I  pair  (or  none)  . 

(Class  II) 

(Class  III)                        (Class  IV) 

Arachnida.                         Myriapoda.                            Insecta. 

i.  Head. 

Parts  of      ^       i  i.   Head-thorax.     , 
Two           ...                    Many. 
Body.               (  2.  Abdomen. 

Other  rings                  r  I.   Head. 
all  alike.       Three  <  2.  Thorax. 
2.  Body  worm-              (  3.  Abdomen. 

like. 

Legs.                       4  pairs.                          Many  pairs.     .                    3  pairs. 

Antennae.                 None.                            i 

pair.                                   i  pair. 

Jaws.                        2  pairs.                          2  or  3  pairs.                          2  pairs. 

CHAPTER  VI. 
BRANCH   ANNULATA. 

THE   SEGMENTED   WORMS. 
Example  — The  Earthworm. 

Habits  of  Earthworms.  —  The  name  "  earthworm  "  is  so 
appropriate  that  no  one  questions  its  fitness.  As  every  one 
knows,  the  earthworm  burrows  through  the  soil,  usually 
making  the  hole  deep  enough  to  reach  moist  earth.  The 
first  portion  of  the  burrow  is  usually  vertical,  but  deeper 
its  course  is  somewhat  irregular.  The  worms  swallow  the 
soil,  and  from  it  they  derive  a  considerable  part  of  their 
food,  digesting  out  of  it  the  organic  matter,  which  is  largely 
composed  of  decaying  plant  material.  The  earthworm  has 
the  advantage  of  utilizing  as  food  the  material  which  it 
must  excavate  to  make  its  burrow.  In  this  respect  it  has 
a  decided  advantage  over  such  animals  as  the  mole  or 
pouched  gopher,  which,  as  they  proceed,  are  obliged  to 
carry  out  or  push  aside  the  soil  without  deriving  any 
immediate  benefit  from  it.  Earthworms  are  nocturnal  in 
their  habits,  and  the  fact  that  they  are  seldom  seen  except 
when  dug  up  leads  most  people  to  suppose  that  they  spend 
their  whole  lives  beneath  the  soil.  But  this  is  not  the  case, 
for  if  one  searches  for  them  with  a  lantern,  they  may  be 
found  in  summer  nights,  sometimes  wholly  out  of  their 
holes,  sometimes  partly  out,  holding  fast  to  the  sides  of  the 
burrow  by  the  tail  end,  and  ready  to  retreat  at  the  approach 
of  danger.  If  they  are  found  crawling  about  in  the  day- 

87 


88  Descriptive  Zoology. 

time,  except  after  a  heavy  rain,  it  is  pretty  good  evidence 
that  they  are  diseased.  Of  ten  %  in  such  cases  it  is  found 
that  they  have  been  parasitized  by  a  fly.  Nearly  every 
one  must  have  noticed  in  the  morning  the  fresh  excrement, 
at  the  mouths  of  their  burrows.  These  coiled  "castings," 
as  they  are  called,  are  the  residue  of  digestion,  and  as  the 
amount  of  nourishment  in  the  soil  is  not  great,  and  since 
the  worm  must  do  considerable  excavating,  the  amount  of 
the  "castings"  is  necessarily  considerable.  In  dry  wea- 
ther the  worms  dig  deep,  and  may  be  several  feet  from  the 
surface.  But  when  the  ground  is  fairly  moist  they  often 
remain  during  the  day  near  the  surface,  with  one  end  near 
the  end  of  the  hole.  In  winter  they  hibernate  below  the 
reach  of  frost. 

Form  of  the  Earthworm.  —  The  end  that  usually  goes 
foremost  is  the  anterior  end,  and  the  hinder  end  is  the 
posterior  end.  When  crawling  on  the  ground  the  surface 
on  which  the  worm  rests  is  the  ventral  surface,  and  the 
surface  uppermost  is  the  dorsal  surface.  If  the  earthworm 
were  split  lengthwise  in  the  middle  line  by  a  vertical  plane, 
the  right  and  left  halves  would  be  counterparts  of  each 
other,  that  is,  the  earthworm  is  bilaterally  symmetrical. 
The  earthworm  is  approximately  cylindric,  the  anterior 
end  being  more  pointed,  and  the  posterior  end  somewhat 
flattened,  especially  on  the  ventral  surface.  The  division  of 
the  body  into  rings,  or  segments,  is  very  evident.  Toward 
the  anterior  end  is  a  region  of  about  six  segments  in  which 
the  sides  and  dorsal  portions  of  the  segments  are  swollen 
and  more  or  less  fused  together,  forming  a  wide  girdle 
called  the  clitellum,  the  function  of  which  is  to  secrete 
the  capsule  in  which  the  eggs  are  laid. 

General  Plan  of  Structure.  —  As  just  noted,  the  body  of  the 
earthworm  is  cylindric.  At  the  anterior  end  is  the  mouth  and 


Annulata. 


at  the  posterior  end  is 
the  anus.  These  are  the 
two  ends  of  the  digestive 
tube,  which  runs  straight 
through  the  body,  being,  on 
the  average,  about  half  the 
diameter  of  the  body.  The 
body,  then,  consists  of  two 
tubes,the  outer  wall,or  body 
wall,  and  the  digestive  tube; 
the  outer  tube,  or  body  wall, 
narrowing  till  it  joins  the 
inner  tube.  Between  these 
two  tubes  is  a  space,  the 
body  cavity,  or  celom.  In 
most  of  the  higher  animals 
we  find  a  similar  space 
around  the  digestive  tube 
and  within  the  body  wall. 
In  the  earthworm  the  body 
cavity  is  divided  into  many 
compartments  by  the  par- 
titions that  extend  between 
the  inner  and  outer  tubes 
at  the  constrictions,  seen 
on  the  outside,  between  the 
successive  segments. 

The  Body  Wall. —This 

consists  of  two  coats,  each 
of  which  is  made  up  of  two 
or  more  layers.  Outside  is 
the  skin,  and  within  this 
the  muscular  coat. 


90  Descriptive  Zoology. 

The  Skin.  —  This  consists  of  two  layers.     Outside  is  the 
cuticle,  a  thin  layer,  usually  showing  a  beautiful  iridescence. 
The  cuticle  often  peels  off  in  specimens  that  have  been  in 
alcohol.     Underneath  the  cuticle  is  the  epidermis  (often1 
called  the  hypodermis). 

The  Muscular  Coat.  —  The  muscular  coat  is  very  much 
thicker  than  the  skin.  It  consists  of  two  layers,  —  an  outer 
layer  of  circular  muscle  fibers,  and  an  inner  layer  of  fibers 
running  lengthwise.  The  inner  layer  is  much  thicker  than 
the  outer. 

The  Bristles.  —  The  bristles,  or  setce,  are  short,  stiff,  chi- 
tinous  spines,  in  four  rows  along  the  ventral  surface  and 
lower  part  of  the  sides.  They  are  outgrowths  of  the  skin, 
and  are  lodged  in  infoldings,  or  pockets,  of  the  cuticle,  which 
are  called  setigerous  glands.  As  the  bristles  are  worn  out 
and  become  useless,  they  are  replaced  by  others ;  and  in 
the  same  sac  may  be  found  bristles  in  various  stages  of 
development.  Each  row  of  bristles  is  double ;  and  each 
segment,  except  the  first  and  last,  has  four  pairs  of  them. 
Special  muscles  are  attached  to  the  base  of  the  sac  hold- 
ing the  bristles,  so  that  the  bristles  can  be  turned  and  held 
in  various  directions.  The  bristles  can  also  be  protruded 
and  withdrawn. 

How  the  Earthworm  Crawls.  — When  the  worm  wishes  to 
crawl  forward,  the  spines  are  turned  backward.  Then  the 
longitudinal  muscles  shorten,  and  the  posterior  end  of  the 
body  is  pulled  forward,  the  whole  body  becoming  shorter 
and  thicker.  Next  the  circular  muscular  fibers  are  short- 
ened ;  this  narrows  and  elongates  the  body ;  but  as  the 
spines  prevent  any  part  from  being  pushed  backward,  the 
result  is  a  forward  movement.  By  a  repetition  of  these 
acts  the  worm  effects  its  slow  locomotion.  If  it  wishes  to 


Annulata. 


91 


travel  with  the  pos- 
terior end  fore- 
most, as  it  does 
occasionally,  it  has 
but  to  point  the 
spines  forward, 
and  the  same  action 
of  the  muscles  will  | 
propel  it  posterior 
end  foremost.  If  * 

w 

the    worm    were  jf 

lying  on  a  perfectly  |  3 

smooth  surface,  on  »  ^ 

which    there    was  1" 

C      C/2 

no  friction  what-  »•  * 
ever,  the  shorten-  |  " 

O      ^ 

ing  and  lengthen-  jg  £ 
ing  of  the  body  |  § 
would  avail  noth-  <r  ^ 

n      90 

ing     in     the    way      5-  g 
of    locomotion;    it      »'  | 
would    be    simply      S.  s 
motion.    The  loco- 
motion of  the  earth-     "|. 
worm,  however,  is      | 
not     essentially      | 
different  from  that 
of   other   animals, 
—  they    must     all 
have  some  point  of 
support   or   resist- 
ance by  means  of 
which     they    pro- 


9.2  Descriptive  Zoology. 

gress.  Most  animals  move  forward  by  pushing  backward 
on  some  more  or  less  solid  support ;  the  earthworm  pulls, 
rather  than  pushes,  itself  along. 

What  the  Earthworm  Eats.  —  Besides  eating  the  soil,  the 
earthworm  eats  leaves,  both  fresh  and  decayed,  decaying 


Circular  muscle  fibers. 


Longitudinal 
muscle  fibers. 


Kidney 


VENTRAL  BLOOD  TUBE 
NERVE  CORD 


Kidney 
pore 


Bristles. 


FIG.  60.    CROSS  SECTION  OF  EARTHWORM. 


wood,  etc.  The  worms  drag  leaves  into  their  holes,  where 
they  are  moistened  by  a  secretion  that  prepares  them  for 
digestion.  Earthworms  eat  bits  of  meat  that  are  left  in 
their  way,  and  would  seem  to  be  almost  omnivorous. 

The  Digestive  System  of  the  Earthworm.  —  The  mouth  is 
a  small  crescent-shaped  opening  on  the  ventral  surface  of 
the  first  segment.  Overhanging  the  mouth  is  a  small  pro- 
boscis. There  are  no  teeth,  nor  anything  corresponding  to 


Annulata.  93 

them.  The  first  part  of  the  digestive  tube  is  the  pharynx, 
very  muscular  and  thick-walled.  Its  own  muscular  fibers 
enable  it  to  close  with  considerable  force.  Attached  to  the 
outside  of  the  pharynx  are  muscles  radiating  in  all  direc- 
tions to  the  outside  of  the  body  wall,  by  means  of  which  the 
pharynx  can  be  retracted  and  dilated.  The  pharynx  not 
only  serves  in  swallowing,  but  is  the  worm's  only  organ  of 
prehension.  By  means  of  the  sucking  and  holding  power 
of  the  pharynx  the  earthworm  is  able  to  drag  relatively 
heavy  leaves  into  the  burrow.  It  is  by  the  strength  and 
various  movements  of  the  pharynx  that  the  worm  performs 
the  work  of  burrowing.  The  pharynx  extends  back  about 
six  segments.  Back  of  the  pharynx  is  the  gullet,  a  slender 
tube  running  to  about  the  thirteenth  or  fourteenth  segment. 
Along  the  sides  of  the  gullet  are  the  esophageal  glands, 
whose  limy  secretion  is  supposed  to  aid  in  digestion.  At 
about  segment  fifteen  the  gullet  dilates  into  the  large,  thin- 
walled  crop.  Separated  from  the  crop  by  a  slight  constric- 
tion is  the  gizzard,  which  extends  about  two  segments. 
The  walls  of  the  gizzard  are  very  thick  and  muscular,  and 
it  has  a  tough  chitinous  lining.  In  it,  by  the  aid  of  sand, 
the  worm  grinds  food,  as  the  hen  does  by  means  of  bits  of 
gravel,  thus  making  up  for  the  absence  of  teeth.  Beyond 
the  gizzard,  the  intestine  extends  to  the  anus,  which  is  a 
vertical  slit  at  the  posterior  end.  The  intestine  is  about 
the  same  diameter  throughout,  except  that  it  is  constricted 
at  each  partition,  and  bulges  out  in  each  segment. 

If  a  cross  section  of  the  intestine  be  made,  it  will  be 
found  that  the  hollow  is  not  circular,  as  would  naturally  be 
expected  from  the  external  form,  but  is  crescent-shaped, 
with  the  concave  side  of  the  crescent  uppermost.  This  is 
due  to  a  prominent  ridge  that  projects  downward  from  the 
upper  inner  surface  of  the  intestine.  This  ridge  is  called 


94  Descriptive  Zoology. 

the  typhlosole.     It  is  richly  supplied  with  blood  tubes  and 
serves  to  increase  the  surface  for  the  absorption  of  food. 

As  the  food  passes  along  the  digestive  tube  it  has  added 
to  it  liquids  secreted  by  the  intestinal  walls,  and  these 
juices  have  the  power  to  digest  starchy,  fatty,  and  proteid 
foods.  As  the  food  is  digested  it  is  absorbed  through  the 
intestinal  walls,  either  into  the  liquid  of  the  body  cavity, 
or  into  the  blood  tubes  that  branch  through  the  walls  of  the 
intestine,  or  into  both  of  these. 

The  Blood.  —  The  blood  of  the  earthworm  is  red,  and  the  , 
red  color  is  due  to  a  substance  called  hemoglobin,  as  in 
human  blood.  But  the  color  is  in  the  liquid  itself,  and  not 
in  the  corpuscles  as  in  our  blood.  Small  colorless  corpus- 
cles are  present  in  the  blood.  The  liquid  found  in  the 
body  cavity  has  also  corpuscles,  and  this  liquid  is  compara- 
ble to  the  lymph  of  higher  animals.  It  is  colorless  or 
sometimes  milky  in  appearance.  There  is  a  minute  pore 
opening  in  the  dorsal  part  of  most  of  the  segments. 

Circulation  of  the  Blood.  —  In  watching  the  live  earth- 
worm one  sees  a  dark  red  streak  through  the  dorsal  wall ; 
this  is  the  dorsai  blood  tube.  It  usually  shows  plainly  a 
wavelike  motion  running  from  the  posterior  end  to  the 
anterior  end.  The  action  is  due  to  the  successive  short- 
ening of  the  circular  muscle  fibers  in  the  wall  of  the 
blood  tube,  from  behind  forward.  This  sort  of  action  is 
familiar  to  many  under  the  name  of  peristaltic  action, 
such  as  takes  place  in  the  intestines  of  most  animals.  By 
this  action  the  blood  is  continually  driven  forward  in  this 
blood  tube.  A  similar  blood  tube  is  to  be  found  under 
the  intestine,  the  ventral  blood  tube.  In  it,  by  the  same 
means,  the  blood  is  sent  backward.  These  are  the  princi- 
pal longitudinal  blood  tubes,  but  there  are  three  small 
tubes  close  to  the  nerve  cord.  In  the  region  of  the  gullet 


Annulata.  95 

are  several,  usually  five,  branches  that  connect  the  dorsal 
and  ventral  blood  tubes  ;  they  arch  around  the  gullet  on 
each  side,  hence  are  designated  the  "aortic  arches";  in 
some  forms  they  have  a  series  of  enlargements,  presenting 
a  necklace-like  appearance.  These  enlargements  contract 
and  dilate  rhythmically,  hence  they  are  sometimes  called 
"  hearts,"  but  they  probably  have  no  greater  share  in  the 
work  of  propelling  the  blood  than  the  other  blood  tubes. 
Connected  with  these  main  blood  tubes  are  branches  by 
which  blood  is  supplied  to  the  body  walls,  to  the  walls  of 
the  digestive  tube,  to  the  partitions  between  the  segments, 
to  the  kidneys,  and  all  the  organs  of  the  body. 

One  earthworm  common  in  the  central  states  has  two 
dorsal  blood  tubes  (hence  the  name,  Diplocardia).  This  is 
a  large  worm  whose  girdle  extends  from  the  I3th  to  the 
1 8th  segment.  It  has  two  gizzards. 

How  the  Earthworm  Breathes. — The  earth  worm  breathes 
by  means  of  the  skin,  there  being  no  special  organs 
of  respiration.  The  body  wall  is  richly  supplied  with  a 
fine  network  of  blood  tubes.  These  are  separated  from 
the  external  air  by  a  thin  membrane  only.  This  thin 
and  delicate  covering  is  always  moist,  and  through  it  an 
interchange  is  continually  taking  place  between  the  blood 
within  and  the  air  without ;  oxygen  is  being  absorbed  into 
the  blood,  while  carbon  dioxid  and  other  waste  matters 
are  passing  in  the  opposite  direction.  The  worm  cannot 
live  long  in  a  warm,  dry  air,  for,  when  the  skin  cannot  be 
kept  moist,  respiration  is  stopped  and  the  worm  is  suffo- 
cated. They  can  endure  immersion  in  water  for  some 
time,  but  it  seems  injurious  to  them.  They  often  are 
found  crawling  about  in  large  numbers  after  a  heavy  rain. 

The  Excretory  System  of  the  Earthworm.  —  Part  of  the 
waste  matter,  the  carbon  dioxid,  is  thrown  off  by  the  skin, 


96  Descriptive  Zoology. 

as  we  have  just  noted.  There  is  also  in  each  segment 
(except  a  few  at  the  two  ends  of  the  body)  a  pair  of  simple 
kidneys,  Each  kidney  is  a  tube  opening  freely  into  the 
body  cavity  at  its  inner  end,  while  the  other  end  opens  to 
the  outside  through  a  small  aperture  in  the  body  wall  below 
(or  sometimes  above)  the  upper  row  of  bristles.  This  long 
tubular  kidney  is  thrown  into  loops,  and  there  is  consider- 
able variation  in  its  diameter  at  different  points.  Each 
tube  begins  as  an  open  funnel  which  is  lined  with  cilia. 
The  oddest  fact  about  these  tubes  is  that  each  kidney  begins 
in  one  segment  and  ends  in  another;  the  funnel  is  in  the 
back  part  of  the  segment  and  the  tube  from  it  soon  passes 
through  the  partition  behind  it,  the  bulk  of  the  tube  lying 
in  the  segment  posterior  to  the  one  in  which  it  began. 
These  tubes  absorb  waste  matter  from  the  liquid  of  the 
body  cavity,  and  convey  it  to  the  outside. 

The  Nervous  System  of  the  Earthworm.  —  This  is  a  chain 
of  nerve  centers  or  ganglions  along  the  ventral  part  of  the 
body  cavity,  lying  under  the  intestine.  In  each  segment  is 
a  ganglion,  and  these  are  connected  by  a  nerve  cord  run- 
ning lengthwise.  Though  apparently  single,  the  nerve  cord 
and  chain  are  really  double,  the  two  ganglions  and  cords 
being  so  closely  applied  and  fused  that  they  appear  as  one. 
The  shortness  of  the  segments  brings  the  successive  gan- 
glions so  near  together  that  they  are  not  very  distinct.  In 
the  anterior  region  the  double  nature  of  the  cord  is  appar- 
ent. Under  the  anterior  part  of  the  pharynx  the  two  strands 
of  the  cord  separate,  one  passing  up  on  each  side  of  the 
pharynx  to  a  large  ganglion,  the  two  ganglions  lying  closely 
side  by  side,  forming  the  "brain."  Thus  a  ring  is  formed 
around  the  pharynx,  which  is  called  the  "  nerve  ring  "  or 
"  esophageal  collar."  From  all  the  ganglions  nerves  pro- 
ceed to  the  surrounding  organs. 


Annulata.  97 

The  Senses  of  the  Earthworm.  —  The  sense  of  touch  is 
undoubtedly  most  fully  developed,  and  on  this  sense  the 
worm  largely  depends  for  its  knowledge  of  the  outer 
world. 

The  sense  of  taste  exists,  and  probably  smell  also,  for 
the  earthworm  exercises  choice  of  various  foods  offered  it, 
as  shown  in  many  experiments  made  by  Darwin. 

The  earthworm  can  distinguish  between  light  and  dark- 
ness, as  evidenced  by  the  fact  that  it  retires  to  its  burrow 
at  the  approach  of  day.  When  a  strong  light  is  flashed 
upon  the  anterior  end  of  the  earthworm,  it  retreats.  The 
posterior  end  is  also  sensitive  to  light.  But  there  is  no 
reason  for  supposing  that  the  worm  sees  objects  with  any 
distinctness,  as  do  animals  with  well-developed  eyes.  There 
is  no  evidence  of  a  sense  of  hearing. 

Development  of  the  Earthworm.  —  The  ovaries  are  small 
and  close  to  the  ventral  surface,  usually  in  the  thirteenth 
segment.  The  oviducts  open  on  the  fourteenth  segment. 
The  eggs  are  inclosed  in  capsules  of  albuminous  material 
formed  by  the  girdle,  or  clitellum.  In  May  and  June  the 
capsules  containing  the  eggs  of  one  species  are  deposited 
in  the  earth  under  logs  and  stones,  or  especially  in,  or 
under,  manure  heaps.  The  little  worms  are  about  an  inch 
long  when  hatched. 

Enemies  of  the  Earthworm.  —  The  principal  enemies  of  the  earth- 
worm are  moles  and  birds.  To  escape  the  latter  the  worms  usually 
retire  into  their  holes  at  the  approach  of  day,  often  plugging  the  mouth 
of  the  hole  with  pebbles.  If  they  are  too  slow  in  hiding,  or  neglect  to 
shut  the  door,  the  sharp  eyes  of  the  bird  may  discover  them.  The 
early  bird  gets  the  late  worm. 

Distribution  of  Earthworms.  —  Earthworms  are  very  widely  dis- 
tributed, being  found  nearly  all  over  the  world,  even  in  isolated  islands 
of  the  ocean.  There  are  many  species,  but  they  are  all  much  alike  in 
most  features  which  are  essential  for  our  present  knowledge. 


98  Descriptive  Zoology. 

Effect  of  Earthworms  on  the  Soil.  —  Darwin  says  that  in  all  regions 
where  there  is  found  a  smooth  expanse  of  vegetable  mold,  which  is 
the  substance  of  all  black  soils,  this  mold  has  passed  and  will  pass 
again,  every  few  years,  through  the  bodies  of  earthworms.  Before  the 
observations  and  experiments  of  Darwin  the  world  hardly  dreamed 
what  an  important  part  earthworms  have  played  in  making  the  soil  what 
it  is,  but  some  previous  observers  had  an  inkling  of  it.  The  quality 
of  the  soil  is  altered  by  the  digestive  process.  It  is  worked  over,  and 
the  deeper  layers  are  brought  to  and  deposited  upon  the  surface.  This 
inversion  of  the  soil  is  essentially  the  same  as  that  of  plowing,  so,  as 
Thomson  says,  earthworms  were  plowers  before  the  plow.  The  holes 
also  aid  circulation  of  air  and  water  in  the  soil.  To  get  a  clear  idea  of 
the  effects  of  these  worms  on  the  soil,  the  student  should  read  Darwin's 
Vegetable  Mould  and  Earthworms. 

Number  of  Earthworms  and  Extent  of  their  Work.  —  Darwin  esti- 
mated that  in  the  tillable  soil  of  England  there  were,  on  the  average,  over 
fifty  thousand  earthworms  to  the  acre  ;  that  they  bring  up  eighteen  tons 
of  soil  to  the  acre ;  that  they  cover  the  surface  at  the  rate  of  an  inch  in 
five  years ;  and  that  thus  in  long  ages  they  have  buried  large  rocks  and 
ancient  buildings.  And  his  conclusion  is  that  "it  may  be  doubted 
whether  there  are  many  other  animals  which  have  played  so  important 
a  part  in  the  history  of  the  world  as  have  these  lowly  organized  ani- 
mals.11 In  the  United  States  earthworms  are  not  so  numerous. 

Harm  done  by  Earthworms.  —  Earthworms  do  some  harm  by  eating 
tender  seedlings  and  delicate  roots,  but  this  is  trifling  in  amount  as 
compared  with  the  very  great  aid  they  render  to  agriculture. 

Repetition  of  Parts.  —  If  a  person  had  grown  up  without  having  seen 
an  earthworm,  at  first  sight  of  one  he  would  probably  be  impressed  with 
its  sameness  of  structure,  nearly  all  the  rings  or  segments  having  the 
same  general  appearance.  Dissection  shows  that  the  internal  structure 
is  not  so  very  different,  the  anterior  portion  having  somewhat  of  a 
variety  in  the  development  of  the  parts  of  the  digestive,  circulatory,  and 
reproductive  organs.  Back  of  the  middle  of  the  body  there  is  no  seg- 
ment which  adds  anything  new  in  function  to  the  body,  each  segment 
being  simply  a  repetition  of  what  precedes.  As  a  rule,  multiplicity  of 
parts,  without  corresponding  variety  of  structure  and  function,  marks  an 
animal  as  low  in  rank. 

Recovery  after  Mutilation.  —  When  an  earthworm  is  cut  in  two  in  the 
middle,  the  anterior  end  probably  lives  in  most  cases,  as  it  has  all  the 


Annulata. 


99 


kinds  of  parts  or  organs  that  the  earthworm  possesses ;  it  has  simply 
lost  a  part  of  the  intestine,  nerve  cord,  blood  tubes,  etc.,  but  not  all  of 
any  one  set  of  organs. 

Color  of  the  Earthworm.  —  The  color  of  the  earthworm  is  largely  due 
to  the  color  of  the  blood  and  to  the  matter  contained  within  the  diges- 
tive tube.  But  besides  this,  the  dorsal  surface  is  darker  than  the  ven- 
tral, as  is  the  case  with  most  animals. 

The  Sandworm.  —  One  of  the  commonest  of  the  sea 
worms  (Nereis)  is  known  as  the  sandworm  or  clam  worm. 
It  is  cylindric,  bluish  green,  and  from  six  inches  to  a  foot 


FIG.  61.    A  MARINE  WORM. 

A,  appearance  at  breeding  season,  and  B,  at  other  times. 
From  Jordan  and  Heath's  Animal  Forms. 

long.  It  is  abundant  along  the  Atlantic  coast,  and  is  an 
excellent  type  to  study,  especially  when  the  earthworm 
cannot  be  readily  obtained.  One  can  usually  find  them  at 
low  tide  along  the  sandy  or  muddy  beaches.  They  make 
burrows  in  the  sand,  but  they  are  to  be  found  at  night, 
swimming  freely,  especially  during  the  breeding  season. 

One  of  the  first  points  of  difference  between  Nereis  and 
the  earthworm  is  that  Nereis  has  a  distinct  head.  On  the 
top  of  the  head  are  two  pairs  of  eyes.  There  are  also  sev- 
eral pairs  of  antennae  and  a  pair  of  palps.  Back  of  the 


ioo  Descriptive  Zoology. 

head  the  segments  are  all  alike.  On  each  side  of  every 
segment  are  muscular  projections,  called  parapodia ;  each 
parapodium  has  several  lobes,  and  these  lobes  are  provided 
with  bundles  of  bristles,  capable  of  extension  and  retrac- 
tion, and  also  of  being  turned  in  different  directions,  as  in 
the  case  of  the  bristles  of  the  earthworm.  By  means  of 
the  parapodia  and  bristles  the  sandworm  can  crawl,  and  it 
also  swims  by  the  same  means.  In  the  middle  region  of 
the  body  the  parapodia  serve  as  gills,  and  the  blood  flowing 
in  the  thin  projections  gives  them  a  red  color. 

The  internal  structure,  in  the  main,  is  very  much  like 
that  of  the  earthworm.  The  pharynx  is  muscular,  and  is 
everted  in  seizing  food ;  but  the  sandworm  has  a  pair  of 
strong,  hard,  horny  teeth,  with  which  it  can  grasp  and  kill 
other  worms  and  small  animals  that  it  eats.  It  also  con- 
sumes vegetable  food.  It  is  itself  a  favorite  morsel  for 
many  kinds  of  fish,  and  hence  is  much  used  by  fishermen 
as  bait. 

The  Leech.  —  Leeches  are  usually  flattened.  They  have  no  spines 
nor  appendages  of  any  sort.  There  are  from  one  to  five  pairs  of  eyes 
on  the  anterior  segments.  The  body  appears  to  have  many  segments, 
but  dissection  shows  that  many  of  these  grooves  are  mere  external 
wrinkles,  there  being  but  one  partition  for  from  three  to  five  of  the  con- 
strictions. There  is  always  a  sucker  at  the  posterior  end,  and  in  some 
leeches  one  at  the  anterior  end  also,  as  in  the  well-known  medical  leech 
of  Europe,  formerly  much  used  in  bloodletting.  The  mouth  has  three 
radiating  jaws,  each  bearing  many  fine  teeth  on  its  edge.  The  jaws  are 
acted  on  by  muscles  which  work  them  back  and  forth  like  a  semicir- 
cular saw.  The  blood  thus  obtained  is  sucked  into  a  crop,  which 
makes  up  the  principal  part  of  the  digestive  tube.  The  crop  has  several 
pairs  of  side  pouches  in  which  the  blood  is  stored,  and  it  is  said  that  the 
leech  can  take  enough  at  one  meal  to  last  a  year.  The  blood  does  not 
coagulate  in  the  crop,  and  this  is  said  to  be  due  to  the  action  of  the 
saliva.  Digestion  is  accomplished  in  the  narrow  stomach  posterior  to- 
the  crop.  A  short  intestine  succeeds  the  stomach.  Leeches  have  three 


Annulata.  101 

modes  of  locomotion :  (a)  they  creep  along  with  a  gliding  movement 
like  a  snail ;  (6)  they  swim  by  a  graceful  undulatory  motion  ;  (c)  they 
travel  by  a  "  looping "  action,  somewhat  as  in  "  measuring  worms," 
holding  on  alternately  by  the  anterior  and  posterior  suckers,  some 
leeches  thus  progressing  actively. 

Other  Annulate  Worms.  —  There  are  many  annulate  worms,  mostly 
marine.  Some  are  free-swimming,  while  others  live  in  tubes  which 
they  form  of  mud,  sand,  or  limestone.  Many  of  them  have  beautiful, 
feathery  gills,  sometimes  distributed  along  the  body,  but  in  the  tube- 
inhabiting  forms  more  frequently  at  the  head  end.  Many  sea  worms 
are  phosphorescent,  emitting  a  vivid  green  light. 

CHARACTERISTICS    OF   ANNULATA. 

1.  The  body  is  bilaterally  symmetrical;   there  are  also 
distinct  anterior  and  posterior  ends,  and  dorsal  and  ventral 
surfaces. 

2.  The  body  is  segmented  (except  Gephyrea). 

3.  There  is  a  distinct  body  cavity,  divided  by  partitions 
into  as  many  compartments  as  there  are  segments. 

4.  There  is  a  well-developed  blood-tube  system  for  the 
circulation  of  blood. 

5.  A  nervous  system  is  present,  consisting  of  cerebral 
ganglions,  esophageal  collar,  and  ventral  nerve  cord. 

6.  There  are  tubular  kidneys  in  each  segment. 

CLASSES  OF  ANNULATA. 

C  i.  Oligochaeta    (few    bristles  —  earth- 
Class  I.  Chaetopoda  (bristle-  J  worm). 

footed).  [2.  Polychaeta  (many  bristles— Nereis). 


Annulata.  - 


Class  2.  Gephyrea. 
Class  3.  Archi-annelida. 
^  Class  4.  Hirudinea  —  the  leeches. 


. 


CHAPTER  VII. . 
BRANCH   MOLLUSCA. 

THE  branch  Mollusca  includes  clams,  oysters,  scallops, 
snails,  slugs,  squids,  and  cuttlefishes.  The  large  majority 
of  mollusks  have  shells.  The  shells  have  always  been 
objects  of  great  interest  on  account  of  their  beauty  of 
color,  delicacy  of  texture,  and  variety  of  form.  Their 
durability  and  the  ease  with  which  a  collection  may  be 
made  and  kept  have  further  contributed  to  making  the 
mollusks  a  favorite  subject  of  study. 

CLASS  PELECYPODA. 
Example.  —  The  Fresh-water  Clam. 

Where  Clams  Live.  —  Clams  live  in  creeks  and  ponds, 
lakes  and  rivers.  They  are  usually  less  abundant  in  the 
smaller  streams,  as  these  may  become  dry  in  midsummer. 
The  natural  position  of  the  clam  is  shown  in  Fig.  64. 

External  Features  of  the  Clam.  — The  clam  shell  is  com- 
posed of  two  equal  valves,  fastened  together  at  the  dorsal 
margin  by  a  tough,  elastic  membrane,  the  hinge  ligament. 
Somewhat  nearer  the  anterior  than  the  posterior  end 
is  a  raised  point  close  to  the  dorsal  margin ;  this  is  the 
umbo ;  it  is  frequently  more  or  less  worn  or  broken  away, 
which  is  not  surprising,  as  it  is  the  oldest  part  of  the  shell 
and  is  subject  to  friction  as  the  clam  plows  along  through 
the  sand.  Around  this  are  the  concentric  lines  of  growth, 
running  parallel  to  the  ventral  margin.  Different  species 

102 


Pelecypoda. 


103 


of  clams  are  distinguished  by  the  size  and  shape  of  the 
shell,  the  relative  proportions  of  the  parts,  the  color  mark- 
ings, smoothness  or  roughness  of  the  shell,  the  thickness 
of  the  shell,  and  by  the  hinge  teeth  on  the  interior. 


Umbo 


Dorsal  margin 
Hinge  ligament 


Line  of  growth 
Ventral  margin 

FIG.  62.    EXTERNAL  FEATURES  OF  A  CLAM  SHELL. 

Outside  of  left  valve. 

The  Inside  of  the  Clam  Shell.  —  After  the  soft  parts  are 
removed,  the  following  internal  markings  are  usually  plainly 
seen.  The  scars  are  the  places  of  attachment  of  the  mus- 
cles, of  which  the  most  notable  are  the  anterior  and  poste- 
rior adductor  muscle  scars.  Just  below  and  posterior  to  the 
anterior  adductor  scar  is  the  scar  of  the  protractor  of  the 
foot.  Above  the  anterior  adductor  scar  is  the  scar  of 
the  anterior  retractor  of  the  foot.  Just  above  and  anterior 
to  the  posterior  adductor  scar  is  the  scar  of  the  poste- 
rior retractor  of  the  foot.  There  are  also  a  few  small  scars 
of  muscles  in  the  dorsal  regions.  In  removing  the  body  of 


104 


Descriptive  Zoology. 


the  clam,  it  will  be  found  that  the  mantle  has  several  mus- 
cular attachments.  Running  parallel  to  and  not  far  from 
the  ventral  margin  is  the  mantle  line,  the  line  of  attachment 
of  the  inner  edge  of  the  muscular  portion  of  the  mantle. 


Anterior 

adductor 

muscle 

\ 


Cardinal 
hinge 


Lateral  hinge  teeth 
I 


Mantle  line 

FIG.  63.    INSIDE  OF  RIGHT  VALVE  OF  CLAM  SHELL. 

The  Hinge  Teeth.  —  In  most  species  of  fresh-water  clams 
there  are  interlocking  projections  near  the  dorsal  margin 
of  the  valves.  Near  the  anterior  adductor  are  strong, 
toothlike  projections,  the  anterior,  or  cardinal,  hinge  teeth. 
Parallel  to  the  dorsal  margin,  near  the  hinge  ligament,  are 
long  ridges,  the  lateral  or  hinge  teeth ;  there  are  usually 
two  of  these  on  one  valve  and  one  on  the  other,  which  fit 
together  when  the  shell  is  closed.  These  teeth  aid  in 
keeping  the  shell  shut. 

The  Natural  Position  of  the  Clam.  —  The  ventral  margin 
is  imbedded  in  the  mud  or  sand,  the  anterior  end  usually 
considerably  deeper  than  the  posterior.  This  position 
brings  the  siphon  openings  above  the  mud ;  but  at 


Pelecypoda. 


105 


times  the  whole  shell  is  buried  in  the  soil ;  this  seems 
to  be  the  case  more  often  in  the  winter,  when  the  clam 
is  less  active,  or  after  freshets  which  cover  the  clams  with 
mud. 

The  Clam  at  Home.  —  By  watching  the  clam  in  its  natural 
habitat  the  position,  as  above  described,  may  be  observed. 
It  may  be  seen  that  the  shell  is  slightly  agape  ;  that  a  soft 
membrane  protrudes  from  the  opened  edges  of  the  shell ; 
that  at  the  posterior  end  are  two  elliptical  openings.  It 
may  be  proved  that  a  current  of  water  is  entering  one  of 
these  openings  and  issuing  from  the  other.  If  the  borders 


FIG.  64.    CLAM  IN  NATURAL  POSITION. 

With  foot  and  siphons  extended. 

of  these  openings  are  touched,  the  soft  membrane  forming 
the  margins  of  the  openings  is  withdrawn  into  the  shell, 
and  the  shell  is  tightly  closed.  If  a  clam,  previously  un- 
disturbed, be  quickly  pulled  out  of  the  mud,  a  soft,  fleshy 


io6  Descriptive  Zoology. 

projection,  the  foot,  is  found  extending  from  the  anterior 
ventral  margin  ;  but  this  will  be  at  once,  though  not  rapidly, 
retracted,  and  the  shell  securely  shut. 

The  Enemies  of  the  Clam.  — The  question  naturally  arises, 
"  Why  does  the  clam  need  such  a  strong  protective  cover- 
ing ? "  The  working  parts  of  the  body  are  soft,  the  Latin 
word  mollis  giving  the  name  to  the  whole  branch  —  Mol- 
lusca.  Such  a  soft-bodied  animal  would  naturally  be  the 
prey  of  carnivorous  animals.  And  further,  since  the  clam 
is  slow  in  movement  and  has  few  and  poorly  developed 
senses  by  means  of  which  to  become  aware  of  the  presence 
of  enemies,  it  is  not  surprising  that  it  should  be  thus 
securely  protected.  Among  his  most  dangerous  foes  are 
the  raccoon,  otter,  mink,  and  muskrat,  and  probably  other 
mammals  that  frequent  the  water  or  prowl  along  the  banks 
of  our  streams.  Muskrats  open  the  shell  by  first  gnawing 
off  the  hinge,  after  which  it  is  comparatively  easy  to  open 
the  shell.  Against  its  enemies  the  clam  has,  apparently, 
but  the  one  means  of  defense,  namely,  to  shut  the  shell  as 
strongly  as  possible  and  to  keep  it  shut  till  the  coast  is 
clear.  Man,  whether  gathering  specimens  for  study,  seek- 
ing pearls,  or  gathering  the  shells  for  buttons,  is  to  be  reck- 
oned among  the  clam's  enemies. 

How  the  Clam  opens  and  shuts  its  Shell.  —  Two  large 
cylindrical  muscles  pass  directly  across  the  body  of  the 
clam,  connecting  the  two  valves.  One  of  these  muscles  is 
at  the  anterior  end,  the  anterior  adductor  muscle,  and  the 
other,  the  posterior  adductor  muscle,  is  at  the  posterior 
end.  The  ends  of  these  muscles  are  strongly  attached  to 
the  inside  of  the  shell.  When  they  shorten  they  bring  the 
two  valves  together  and  hold  them  with  great  force. 

For  an  inch  or  so  along  the  dorsal  margin  the  two  valves 
are  held  together  by  the  elastic  hinge  ligament,  which  is 


Pelecypoda. 


107 


merely  an  uncalcified  portion  of  the  shell.  When  the  mus- 
cles pull  the  valves  together,  this  ligament  is  stretched. 
Consequently,  as  soon  as  the  adductor  muscles  relax,  the 
elasticity  of  the  hinge  ligament  opens  the  shell.  It  will  be 
observed  that  the  shell  is  shut  by  muscular  effort,  whereas 
it  is  opened  by  the  mechanical  action  of  a  spring,  which 
consists  of  practically  dead  tissue.  It  requires  no  effort  to 


Hinge  Ligament 
External 


Hinge  Ligament 
Internal 


FIG.  65.    MECHANISM  FOR  OPENING  AND  SHUTTING  A  CLAM  SHELL. 

keep  the  shell  open.  As  the  shell  is  partially  open  most 
of  the  time,  the  economy  of  this  arrangement  is  apparent. 
Why  would  it  not  do  as  well  to  have  the  shell  opened  by 
muscular  action  and  closed  by  a  spring  ?  In  some  bivalve 
mollusks  the  hinge  ligament  is  internal,  so  that  when  the 
shell  is  shut  the  ligament  is  compressed,  instead  of 
stretched,  as  in  these  clams.  Then,  when  the  muscles 
relax,  the  shell  is  opened  by  the  expansive  elasticity  of  the 
ligament.  The  general  principle  is  the  same,  but  is  carried 
out  in  a  different  way.  See  Fig.  65. 


io8  Descriptive  Zoology. 

Why  the  Clam  opens  and  shuts  its  Shell.  —  It  is  only  by 
opening  the  shell  that  the  clam  is  able  to  place  itself  in 
communication  with  the  outside  world.  The  opening  allows 
the  foot  and  siphons  to  be  protruded.  When  disturbed,  the 
clam  withdraws  the  foot  and  the  siphons,  and  completely 
closes  the  shell,  and  usually  remains  in  this  condition  until 
the  disturbance  ceases.  The  muscles  are  of  the  slow-acting, 
non-striped  kind,  and  can  remain  shortened  a  long  time ; 
but  they  evidently  get  tired,  and  after  a  while  they  relax, 
and  the  shell  gapes  open. 

The  Location  of  the  Siphons.  —  Since  the  clam  pulls  itself 
forward  by  the  foot,  which  it  imbeds  in  the  mud,  the  foot 
naturally  extends  forward  and  downward.  As  a  good  share 
of  the  ventral  part  of  the  shell  is  below  the  level  of  the  sand 
or  mud,  the  only  available  place  to  take  in  clear,  fresh  water 
is  at  the  upper  and  posterior  border.  And  here  we  find 
the  siphons. 

How  the  Clam  Progresses.  —  The  foot  is  slowly  extended 
forward  and  downward  into  the  mud.  When  it  has  become 
well  imbedded  in  the  mud,  if  the  clam  wishes  to  move  for- 
ward, it  shortens  the  muscles  of  the  foot  and  body,  and  thus 
pulls  forward  the  body,  shell  and  all.  Then  another  inter- 
val must  elapse  until  the  foot  is  again  anchored  before  an- 
other move  can  be  made.  In  this  way  the  clam  slowly 
plows  its  way  along,  leaving  a  distinct  furrow  by  which 
it  may  be  traced  in  clear  water.  The  protruding  of  the  foot 
is  a  slow  process,  while  the  act  of  pulling  forward  is  of  com- 
paratively short  duration.  It  is  stated  that  the  extension  of 
the  foot  is  mainly  due  to  an  inflow  of  blood  which  is  kept 
from  returning  by  a  tightening  of  the  sphincter  muscles 
around  the  veins.  At  any  rate,  the  foot  is  often  found 
dilated  toward  the  extremity,  which  plainly  increases  its 
efficiency  as  an  anchor. 


Pelecypoda.  109 

Extent  of  the  Clam's  Locomotion.  —  The  clam  does  not 
travel  far.  Since  it  brings  its  food  in  by  the  currents  of 
water  which  it  creates,  it  does  not  have  to  move  about  for 
food.  When  the  water  gets  low,  as  in  most  creeks  in  the 
summer  time,  the  clam  apparently  seeks  the  deeper  water. 
The  question  naturally  arises,  "How  does  the  clam  become 
aware  of  this  change,  and  how  does  it  know  in  what  direc- 
tion to  go  ? " 

The  Clam's  Muscles  and  their  Functions.  —  There  are  five 
chief  muscles :  — 

I.  Anterior  adductor.    >  ...      See  Figs.  63 

>    Close  the  shell. 
-  2.  Posterior  adductor.   >  and  65. 

3.  Protractor  —  pulls    the   foot   and   body  forward  and 
downward. 

4.  Anterior  retractor  —  pulls  foot  and  body  upward  and 
backward. 

5.  Posterior  retractor  —  pulls  foot  and  body  upward  and 
backward. 

When  the  foot  is  imbedded  in  the  sand  or  mud,  the 
shortening  of  the  retractors,  whose  fibers  spread  over  the 
body  and  foot,  pull  the  shell  forward  instead  of  retracting 
the  foot. 

Structure  of  the  Clam  Shell.  —  If  a  shell  is  roasted  thor- 
oughly, its  structure  may  more  easily  be  learned.  The  first 
fact  to  be  noted  is  that  the  shell  consists  of  layers ;  the 
next,  that  these  layers  are  in  two  sets,  the  dividing  plane 
between  which  starts  from  the  mantle  line  and  extends 
toward  the  umbo.  The  shell  is  an  outgrowth  of  the  outer 
layer,  or  epidermis,  of  the  mantle.  But  the  layers  of  the 
shell  made  by  the  part  of  the  mantle  outside  of  the  mantle 
line  are  not  directly  continuous  with  the  layers  formed  by 
that  part  of  the  mantle  which  is  dorsal  to  the  mantle  line. 
The  mantle  line  is  really  a  row  of  small  muscle  scars  where 


no  Descriptive  Zoology. 

the  muscular  border  of  the  mantle  is  attached  to  the  shell. 
The  edge  of  the  mantle,  it  was  observed,  is  attached  to  the 
edge  of  the  shell.  The  outermost  layer  of  the  shell,  the 


•  Umbo 

FIG.  66.    STRUCTURE  OF  CLAM  SHELL. 

Cross  section. 

periostracum,  is  formed  by  the  edge  of  the  mantle,  and  is 
horny  in  composition.  Inside  this  is  the  prismatic  layer, 
and  innermost  is  the  laminated  pearly  layer. 

Growth  of  the  Clam  Shell.  —  The  successive  concentric 
lines  of  growth  seen  on  the  outside  of  the  shell  mark  the 
growth,  each  line  of  growth  having  once  been  the  ventral 
edge  of  the  shell.  The  layers  are  formed  by  the  mantle, 
and  each  new  layer  is  a  little  wider  and  longer  than  the  one 
preceding,  and  outside  of  it.  The  muscles  grow  and  gradu- 
ally move  outward,  hence  the  muscle  scar  continually  widens, 
forming  a  triangle.  But  as  the  muscles  move  on,  the  scar 
of  former  years  is  covered  by  the  new  layers  formed  by  the 
mantle. 

Uses  of  the  Clam  Shell.  —  The  fresh-water  clams  are  little 
used  as  food,  but  their  shells  are  used  largely  in  making 
buttons.  This  is  an  industry  of  considerable  extent  along 
the  Mississippi  River  and  some  of  its  tributaries. 

Respiration  in  the  Clam.  —  The  current  of  water  which 
we  saw  entering  and  leaving  the  clam  brings  oxygen  as  well 


Pelecypoda. 


in 


as  food.  The  blood  circulates  in  the  walls  of  the  gills,  and 
thus  the  water  current  and  the  blood  current  are  brought 
very  close  to  each  other.  Oxygen  passes  from  the  water 
into  the  blood ;  and  from  the  blood,  carbon  dioxid  and  other 
waste  matters  pass  into  the  water  through  the  thin  layer  of 
the  wall  of  the  gill  surrounding  the  blood  tubes.  There  is 
also  an  active  circulation  of  blood  in  the  mantle,  and  a  con- 
siderable share  of  the  work  of  respiration  is  undoubtedly 
accomplished  here. 

The  Structure  of  the  Gills.  —  Each  gill  has  the  appearance 
of  a  thin,  single-layered  membrane ;  but  in  reality  each  gill 


Artery 

\ 

Anterior  adduc-    \ 
tor  muscle 


Auricle    Ventricle 

i      ! 


Posterior  adductor 
muscle 


Gill 


FIG.  67.    BODY  OF  CLAM. 

Left  valve  removed. 

is  double  walled,  and  a  cross  section  is  like  a  letter  V. 
Each  gill  is  a  long,  narrow,  V-shaped  pocket  or  trough, 
though  divided  into  many  compartments  by  cross  partitions. 
The  two  gills  of  each  side  are  united  so  as  to  form,  in  cross 
section,  a  W,  the  upper  margin  of  the  outer  wall  of  the 
outer  gill  being  attached  to  the  mantle,  the  upper  edge  of 


112 


Descriptive  Zoology. 


the  inner  wall  of  the  outer  gill  joining  the  upper  edge  of  the 
outer  wall  of  the  inner  gill,  while  the  upper  edge  of  the  inner 
wall  of  the  inner  gill  is  sometimes  attached  to  the  body  or 
sometimes  free.  Back  of  the  body  the  upper  edges  of  the 
inner  gills  of  the  two  sides  unite  with  each  other,  thus  sepa- 
rating the  lower,  or  gill,  cavity,  into  which  the  water  first 


FIG.  68.    CLAM,  SIDE  VIEW. 

Water  currents  to  the  mouth  and  through  the  gills. 

enters,  through  the  lower  incurrent  siphon,  from  the  upper, 
or  cloacal,  chamber,  from  which  the  water  passes  out.  The 
question  presents  itself,  "  How  does  the  water  pass  from 
the  one  cavity  into  the  other  ? " 

The  sides  of  the  gills  are  perforated,  so  much  so  that  they 
are  compared  to  a  sieve  or  trelliswork.  The  vibrations  of 
the  myriads  of  cilia  with  which  the  gills  are  covered  drive 


Pelecypoda.  113 

the  water  that  lies  outside  of  the  gill  through  these  openings 
into  the  space  within  the  gill.  The  water  then  passes  up 
through  the  open  top  of  the  gill  into  the  cloacal  chamber, 
and  back  out  of  the  excurrent  siphon.  The  four  gills  are 
so  many  narrow,  V-shaped  troughs  with  their  sides  full  of 
holes.  Instead  of  filling  at  the  top  and  leaking  out  at  the 
holes  in  the  sides,  these  troughs  are  filled  through  the  holes 


Ventricle 


Cross  section  through  heart.         Cross  section  through  posterior  adductor  muscles. 
Section  at  A .  Section  at  B. 

FIG.  69.    CLAM. 

Water  currents  through  the  gills.     Compare  with  Figs.  68  and  71. 

in  the  sides,  and  overflow  above,  —  only  the  water  cannot 
run  down  the  sides  of  the  trough,  but  must  pass  back  and 
out  through  the  upper  siphon.  (Figs.  68,  69,  and  70.) 

The  Food  of  the  Clam,  and  how  Obtained.  —  The  clam 
lives  on  microscopic  plants  and  animals  and  on  minute  par- 
ticle^ oj[w  organic  matter.  This  material  is  supplied  by  the 
current*of  water  which  is  continually  passing  into  the  lower 


Descriptive  Zoology. 


and  out  of  the  upper  siphon.  The  current  is  produced  by 
the  vibration  of  the  cilia  which  cover  the  outside  of  the  gills 
and  the  inner  surface  of  the  mantle.  The  entering  current 
passes  forward  around  the  body  and  gills.  The  palps  are 
also  ciliated ;  and  between  the  two  palps  of  each  side  the 
minute  particles  are  caught  and  passed  on  into  the  mouth, 


Blood  tubes 


Blood  currents 


FIG.  70.    STRUCTURE  OF  CLAM'S  GILL. 


whose  upper  lip  is  formed  by  a  continuation  of  the  two 
outer  palps  meeting  across  the  middle  line,  the  two  inner 
palps  similarly  forming  a  lower  lip. 

The  Digestive  System  of  the  Clam.  — The  mouth  is  just 
back  of  the  anterior  adductor  muscle.  A  short,  wide 
gullet  extends  upward  and  backward  to  the  large  spherical 


Pelecypoda. 


stomach.  On  each  side  of  the  stomach  is  a  large,  greenish, 
digestive  gland,  often  called  the  liver,  whose  secretion 
passes  into  the  stomach.  From  the  stomach  the  intestine 
passes  downward  and  backward,  making  one  or  two  coils 
in  the  abdomen  and  foot,  then  passes  upward  back  of  the 
stomach,  near  the  dorsal  margin ;  it  then  turns  posteriorly, 
parallel  to  the  dorsal  margin,  passes  through  the  ventricle 


Digestive 
gland 


Anus 


Intestine 

FIG.  71.    DIGESTIVE  AND  EXCRETORY  ORGANS  OF  A  CLAM. 

of  the  heart,  over  the  posterior  adductor  muscle,  just  back 
of  which  it  ends,  thus  discharging  the  refuse  of  digestion 
where  the  outgoing  current  of  water  will  catch  it  and 
sweep  it  out  of  the  body  through  the  dorsal  siphon.  The 
digestive  tube  is  hard  to  trace  in  a  fresh  specimen,  less 
difficult  in  one  which  has  been  boiled  or  hardened  in 
alcohol.  The  whole  tube  may  be  injected  with  a  colored 
starch  injection  and  thus  readily  followed.  In  the  fall 
the  intestine  is  often  found  to  contain  a  cylindrical  body  of 


1 1 6  Descriptive  Zoology. 

clear  material  having  the  consistency  of  a  gumdrop.  This 
is  the  "  crystalline  rod,"  and  is  thought  by  some  to  be  a 
store  of  food  material.  Others  regard  it  as  a  secretion  to 
protect  the  lining  of  the  intestine  from  injury. 

The  Circulatory  System  of  the  Clam.  —  From  the  gills 
and  mantle  of  each  side  the  blood  passes  up  into  the  cor- 
responding auricle  (Figs.  67  and  69).  The  auricles  are 
wide  at  the  base,  where  they  arise  from  the  upper  margins 
of  the  gills,  but  narrow  as  they  approach  the  ventricle,  so 
that  the  lateral  view  gives  a  triangular  appearance.  The 
auricles  are  thin-walled,  delicate  structures.  They  open 
into  the  sides  of  the  median  ventricle.  From  the  ventricle 
arise  two  arteries,  one  carrying  blood  forward  above  the 
intestine,  the  other  extending  backward  beneath  the  intes- 
tine (Fig.  67).  After  leaving  the  arteries,  the  blood 
passes  into  irregular  and  ill-defined  channels,  supplying  all 
parts  except  the  shell.  The  blood  collects  in  a  caval  vein 
under  the  floor  of  the  pericardium,  then  passes  through 
the  kidneys,  and  to  the  gills  once  more.  In  the  gills  and 
mantle  the  blood  loses  carbon  dioxid  and  gains  oxygen. 
As  it  passes  through  the  kidneys  it  loses  nitrogenous  waste 
matter,  and  from  the  digestive  tube  it  absorbs  new  food 
material  for  the  support  of  the  life  processes. 

The  Kidneys.  —  The  kidneys  are  ill-defined,  dark-colored 
organs,  lying  just  beneath  the  floor  of  the  pericardium  and 
in  front  of  the  posterior  adductor  muscle.  Each  kidney 
consists  of  a  tube  doubled  on  itself,  the  bend  being  near 
the  adductor  muscle.  One  end  of  the  tube  communicates 
with  the  bottom  of  the  anterior  part  of  the  pericardium, 
the  other  end  opens  on  the  side  of  the  abdomen,  near  the 
upper  edge  of  the  inner  wall  of  the  inner  gill,  and  above 
the  tip  of  the  corresponding  palp.  Here  the  excretion 
is  poured  out,  and  is  carried  away  by  the  water  current. 


Pelecypoda. 


117 


Nervous  System  of  the  Clam.  —  There  are  three  pairs 
of  ganglions,  which  are  connected  by  nerve  trunks,  called 
commissures  :  — 

1.  The  cerebral   ganglions,   one   on   each   side   of   the 
mouth,  just  above  the  outer  palp  of  each  side;  these  are 
connected  by  a  nerve  cord  which  passes  over  the  gullet. 

2.  The  two  pedal  ganglions,  lying  closely  side  by  side, 
deeply  imbedded  in  muscle,  near  the  middle  of  the  foot. 
Each  of  these  is  connected  with  the  cerebro-pleural  gan- 
glion of  its  side. 

Gullet 


Visceral 
Ganglions 


FIG.  72.    CLAM,  NERVOUS  SYSTEM. 


3.  On  the  under  surface  of  the  posterior  adductor  are 
the  two  visceral  ganglions,  apparently  forming  one  double 
ganglion.  These  ganglions  are  much  easier  to  find  than 
the  others.  Each  of  these  is  connected  with  the  cerebral 
ganglion  of  its  side  by  a  nerve  cord,  which  runs  along  in 
the  dorsal  part  of  the  body  for  a  good  share  of  its  length. 
From  all  of  these  ganglions  nerves  extend  to  supply  the 
adjacent  regions. 


n8  Descriptive  Zoology. 

The  Sense  Organs.  —  The  sense  of  touch  is  preeminent. 
This  sense  is  best  developed  in  the  palps,  along  the  margin 
of  the  mantle,  especially  that  part  of  it  which  forms  the 
borders  of  the  siphons,  and  in  the  foot.  There  is  no 
sense  of  sight,  but  the  tentacles  around  the  siphons  seem 
somewhat  sensitive  to  light.  On  a  nerve  near  the  pedal 
ganglion  is  the  so-called  "ear  sac,"  of  doubtful  use.  At 
the  base  of  the  gills  is  an  organ  sometimes  called  the 
"smelling  patch,"  which,  perhaps,  has  the  office  of  testing 
the  quality  of  the  water.  The  sense  of  taste  is  doubtful, 
though  it  is  probable  that  there  is  some  discrimination  as 
to  what  should  be  taken  as  food.  The  clam  is  sensitive 
to  vibrations  communicated  either  through  the  soil  or  the 
water. 

The  Reproductive  Organs.  —  These  are  diffuse  glands 
enveloping  the  coils  of  the  intestine  in  the  abdomen.  The 
glands  in  the  two  sexes  (ovaries  and  spermaries)  are  so 
similar  that  it  usually  requires  microscopic  examination  to 
distinguish  them.  The  ducts,  both  in  the  male  and  female, 
open  on  the  side  of  the  body  near  the  opening  of  the  duct 
from  the  kidneys.  The  eggs,  when  mature,  pass  out  of 
the  duct  and  lodge  in  the  gills  (more  often  the  outer  gills) 
of  the  female.  They  are  fertilized  by  the  sperms,  which 
have  been  set  free  in  the  water  and  are  drawn  in  by  the 
same  current  that  brings  the  food  particles.  The  males 
and  females  may  sometimes  be  distinguished  by  the  greater 
convexity  of  the  shell  in  the  female,  the  valves  being  more 
bulging  to  accommodate  the  accumulation  of  eggs  and 
young  clams  in  the  outer  gill. 

Development  of  the  Clam.  —  The  young  usually  develop 
during  the  fall  and  winter.  When  liberated,  the  young 
clams  are  called  Glochidia.  They  are  of  different  shape 
from  the  adult,  being  ovate,  with  the  hinge  at  the  wider 


Pelecypoda.  119 

end.  There  is  but  one  adductor  muscle ;  the  foot  is  yet 
undeveloped,  but  from  the  foot  region  project  long  threads, 
the  "  byssus,"  by  which  it  becomes  attached.  At  the  tip 
of  each  valve  there  is  an  incurved  hook  by  which  the  little 
clam  usually  catches  hold  of  the  fin  or  gill  of  a  fish, 
whereby  it  is  protected  from  enemies  and  kept  in  fresh 
water.  Soon  after  it  thus  becomes  attached  it  is  covered 
by  a  growth  of  the  skin  (a  diseased  growth)  which  still 


FIG.  73.    YOUNG  CLAM,  STILL  WITHIN  THE  EGG  MEMBRANE. 

m,  adductor  muscle ;  /,  hooks  by  which  it  attaches  itself  to  the  gills  or  fins  of  fishes ;  b,  byssus ; 

s,  sense  organs. 

further  protects  the  parasite.  When  sufficiently  mature, 
the  young  clam  drops  off,  soon  becomes  like  the  adult  in 
form,  and  shifts  for  itself. 

Salt-water  Clams.  —  Although  several  kinds  of  marine 
clams  are  used  as  food,  there  are  two  that  are  more  largely 
eaten  in  this  country.  One  is  Venus  mercenaries,  found 
from  Texas  to  Cape  Cod,  but  rare  north  of  that  point;  the 
other  Mya  arenaria,  found  generally  along  the  coasts  of 
the  Eastern  states,  but  rather  distinctively  more  Northern 
than  the  other.  So  when  Massachusetts  people  speak  of 
clams  they  mean  the  Mya,  commonly  designated  elsewhere 
as  the  "soft  clam,"  "soft-shelled  clam,"  "long-necked 
clam,"  or  "long  clam."  Whereas,  when  New  Yorkers 
mention  clams,  without  any  qualifying  adjective,  they  have 


120 


Descriptive  Zoology. 


in  mind  Venus  mercenaries,  which,  farther  north,  and  away 
from  the  coast,  would  be  designated  as  the  "  hard  clam," 
"round  clam,"  or  "quahog."  Both  are  frequently  found 
in  the  markets  inland. 

The  Soft-shell  Clam.  —This  clam 
lives  in  a  vertical  burrow  with  the 
anterior  end  down.  Instead  of 
having  short  siphons  like  the  fresh- 
water clam,  the  posterior  margins 
of  the  mantle  lobes  are  extended 
and  grown  together  to  form  a  long 
double  tube,  which  reaches  to  the 
surface  of  the  sand  or  mud,  the  body 
being  sometimes  a  foot  from  the 
surface.  The  two  mantle  lobes  are 
united  along  their  entire  edges, 
except  at  the  two  siphon  apertures 
and  an  anterior  opening,  for  the 
projection  of  the  foot.  The  ventral 
channel  is  the  incurrent  and  the 
smaller  dorsal  one  the  excurrent. 
As  in  the  clam  we  have  studied, 
the  incurrent  siphon  has  a  fringed 
margin  and  is  very  sensitive.  The 
border  is  also  dark  colored,  so  that 
it  is  not  readily  seen,  and  if  disturbed 
it  is  withdrawn  into  the  hole.  At 
low  tide  the  tube  is  generally  so  re- 
tracted. At  this  time  clams  are 
hunted  and  dug  up. 

As  the  clam  grows,  it  deepens  and 
widens  its  burrow.  The  foot  is  small,  and  the  old  clam,  dug 
up  and  left  on  the  surface,  has  difficulty  in  making  a  new 


FIG.  74.  LONG  CLAM,  BURIED 
IN  THE  MUD. 

The  arrows  show  the  currents  in 
the  siphons. 

From  Kingsley's  Zoology. 


Pelecypoda. 


121 


burrow.  The  internal  structure  is  essentially  the  same  as  in 
the  fresh-water  clam.  To  accommodate  the  long  siphon 
tube  when  it  is  retracted,  there  is  a  deep  indentation  of  the 
mantle  line  in  the  posterior  region.  The  shell  of  My  a  can- 
not be  snugly  closed,  there  being  a. gap  both  anteriorly  and 
posteriorly.  Probably  this  may  be  accounted  for  by  the 
more  protected  position  and  the  need  of  having  the  siphon 


FIG.  75.    HARD  CLAM;   ROUND  CLAM;  QUAHOG. 

With  foot,  siphons,  and  edge  of  mantle  extended. 

tube  extended  most  of  the  time.  The  siphon  tube,  with  its 
black  tip,  is  commonly  called  the  "  head,"  but  this  clam  is 
as  headless  as  its  fresh-water  relative.  % 

The  Hard  Clam.  —  The  hard  clam,  or  quahog,  is  also  an 
important  sea-coast  food,  especially  where  the  soft  clam 
is  not  obtainable.  It  is  oval,  with  a  thick  shell.  It  bur- 
rows but  a  short  distance,  hence  the  siphons  are  not  long, 
and  the  two  tubes  are  partly  separated.  The  foot  is  well 
developed,  and  the  clam  crawls  more  or  less  like  the  fresh- 


122  Descriptive  Zoology. 

water  clam.  These  clams  may  be  picked  up  at  low  tide, 
but  are  ordinarily  taken  by  means  of  long  rakes  or  tongs. 
The  smaller  or  medium-sized  ones  are  preferred.  The 
border  of  the  inner  surface  of  the  shell  is  usually  purplish, 
and  this  part  was  made  into  the  beads  which  constituted 
the  more  valuable  purple  wampum  of  the  Indians  of  New 
England. 

The  Oyster.  —  One  essential  difference  between  the 
oyster  and  the  clam  is  that  the  oyster  is  stationary, 
being  firmly  attached  by  one  valve  to  some  solid  object, 
a  rock,  or  another  oyster  so  attached.  The  oyster  lies  on 
the  left  side,  and  the  lower  valve  is  much  more  concave 
than  the  upper,  which  is  nearly  flat,  serving  as  a  lid.  As 
the  oyster  does  not  travel,  it  needs  no  foot  and  has  none, 
hence  is  less  tough  than  the  clam.  The  hinge  is  at  the 
pointed  end  of  the  shell,  and  the  two  mantle  lobes  are  free 
from  each  other,  except  near  the  hinge.  There  are  no 
siphons,  the  water  entering  all  along  the  more  curved  bor- 
der of  the  shell  and  passing  out  on  the  straighter  side  near 
the  larger  end  of  the  shell.  The  water  is  propelled  by  cilia 
and  passes  through  the  gills  as  in  the  clam.  There  is  but 
one  adductor  muscle. 

Development  of  the  Oyster.  —  The  eggs  and  young  are 
not  carried  nor  protected  as  in  the  clam,  but  the  eggs  are 
fertilized  after  being  set  free  in  the  water.  The  egg 
becomes  many-celled  by  the  growth  and  repeated  division 
of  thft  one  cell  w-hich  constituted  the  egg.  This  becomes 
ciliated  and  swims  by  means  of  these  cilia.  After  a  few 
days  of  this  free  swimming  life,  during  which  time  the 
shell  and  other  organs  are  gradually  developing,  the  little 
oyster  attaches  itself  by  its  left  valve  to  some  submerged 
object,  to  which  it  becomes  firmly  cemented  by  the  deposit 
of  limy  material  which  makes  the  hard  part  of  the  shell. 


Pelecypoda.  123 

Comparison  of  Clam  and  Oyster.  —  It  will  be  noticed  that 
the  hinge  in  the  oyster  is  at  on.e  end  of  the  shell.  This 
end  corresponds  to  the  anterior  end  of  the  clam.  The 
oyster  shell  can  open  but  slightly.  The  shells  are  rougher 
than  those  of  clams.  The  green  spot  in  the  oyster  is  the 
digestive  gland  (often  improperly  called  the  liver),  and 
not  the  digestive  tube  or  its  contents,  as  commonly  sup- 
posed. Oysters  and  other  salt-water  mollusks  are  often 
left  above  water  at  low  tide. 

Distribution  of  Oysters.  —  Oysters  are  abundant  along 
the  Atlantic  coast,  south  of  Cape  Cod,  and  in  the  Gulf  of 
Mexico.  In  former  times  they  occurred  north  of  Cape 
Cod,  but  are  now  rare.  Other  species  are  found  on  the 
Pacific  coasts  and  on  the  coasts  of  Europe,  at  the  Cape  of 
Good  Hope,  in  Japan,  and  Australia.  Chesapeake  Bay  is 
the  center  of  the  oyster  industry,  and  the  British  market 
is  now  largely  supplied  from  our  beds,  as  we  have  not  only 
the  most  abundant  supply,  but.  ours  are  the  best  in  the 
world. 

The  Oyster  Season.  —  The  common  saying  that  oysters 
are  good  only  in  months  containing  the  letter  "  r,"  is  partly 
wrong  and  partly  right.  Oysters  are  good  to  eat  at  any 
time  of  the  year  when  freshly  taken  from  the  water.  But 
during  their  breeding  season  —  June  to  August —  they  do 
not  bear  handling  so  well,  and  are  more  likely  to  spbil. 
It  is  more  profitable,  too,  to  leave  them  undisturbed  at  this 
time,  that  they  may  increase  enough  to  maintain  their 
numbers. 

The  Shipworm.  —  As  the  name  implies,  this  mollusk  is  wormlike. 
It  sometimes  becomes  ten  inches  long  and  half  an  inch  thick.  It  bears 
a  small  bivalve  shell  at  its  larger  end.  It  burrows  in  wood,  doing  great 
damage  to  ship  timbers,  buoys,  wharves,  etc.  The  first  stages  of  devel- 
opment are  like  those  of  many  other  bivalves.  If  the  larva  cannot  find 


I24 


Descriptive  Zoology. 


wood,  it  soon  dies.  The  hole  by  which  the  larva  enters  the  wood  is 
hardly  larger  than  a  pin  head,  but  as  the  animal  grows  it  excavates  a 
constantly  widening  tube,  thus  imprisoning  itself  for  life.  Just  how  it 
burrows  is  not  certainly  known.  It  does  not  feed  upon  the  wood,  the 
fine  sawdust  being  carried  off  through  the  excurrent  siphon.  Its  food 
consists  of  microscopic  plants  and  animals,  which  are  brought  in  by 


FIG.  76.    RAZOR  SHELL  CLAM. 

currents,  as  in  the  clam,  and  its  only  communication  with  the  outer 
world  is  through  the  small  hole  by  which  it  first  entered  the  wood. 
Shipworms  work  rapidly,  often  completely  honeycombing  the  wood. 
But  no  matter  how  many  of  them  there  are  in  the  wood,  their  tubes 
never  interfere  with  one  another,  but  there  is  always  left  a  thin  partition 
between.  They  avoid  iron  rust,  so  timbers  are  protected  by  driving 
them  thickly  with  broad-headed  nails.  The  copper  sheathing  of  hulls 
of  ships  is  the  best  protection.  Shipworms  caused  the  famous  dam 
break  in  Holland  at  the  beginning  of  the  last  century. 

The  Razor  Shell  Clam.  —  The  razor  shell  clam  has  a  shell  somewhat 
resembling  in  shape  and  size  the  handle  of  a  razor.     The  foot  projects 

at  the  anterior  end,  the  siphons 
at  the  posterior  end.  These 
clams  make  vertical  holes  in 
the  sand  and  can  dig  rapidly. 
At  low  tide  the  posterior  end 
may  be  seen  projecting  from 
the  sand,  but  unless  the  col- 
lector approaches  quietly  and 
seizes  the  clam  quickly,  it  is 


FIG.  77.    MUSSEL. 

With  threads  by  which  it  is  attached. 


almost  sure  to  escape.  They 
seem  to  be  very  sensitive  to 
vibrations,  and  probably  be- 
come aware  of  approach  through  these  rather  than  through  hearing  or 
sight,  although  they  are  somewhat  sensitive  to  light. 

The  Salt-water  Mussel.  —  One  of  the  most  common  marine  bivalves 
is  the  mussel.     The  shell  is  usually  dark  or  purplish,  and  rather  thin 


Pelecypoda.  125 

and  weak.  The  mussel  is  found  attached  to  rocks  by  means  of  a  num- 
ber of  yellowish  threads,  the  byssus,  which  grow  from  the  base  of  the 
small  foot.  Mussels  are  found  widely  distributed  along  the  coasts  in 
most  seas.  They  are  used  to  a  considerable  extent  as  food  in  some 
countries. 

The  Giant  Clam.  —  Probably  the  largest  bivalve  known  is  a  marine 
clam  of  the  genus  Tridacna,  found  in  Eastern  seas.  The  soft  body 
sometimes  weighs  twenty  pounds,  and  the  two  valves  of  the  shell 
together  may  weigh  five  hundred  pounds. 

The  Scallop.  —  The  outline  of  the  shell  as  seen  from  one  side  is 
nearly  circular.  The  two  valves  are  not  equal,  one  being  less  convex 


FIG.  78.    SCALLOP. 

• 

The  crusaders'  badge. 

than  the  other,  sometimes  perfectly  flat.  While  at  rest  the  scallop  lies 
on  the  bottom  with  its  valves  widely  gaped  open.  The  scallop  has  a 
row  of  eyes  along  the  margin  of  each  mantle  lobe.  When  an  enemy 
approaches,  the  shell  is  quickly  and  powerfully  shut  by  the  one  strong 
adductor  muscle.  This  forcibly  ejects  the  water,  and  by  reaction  the 
scallop  is  driven  through  the  water,  hinge  foremost.  The  foot  is  rudi- 
mentary or  lacking.  The  scallop  is  used  for  food  ;  the  adductor  muscle. 


126  Descriptive  Zoology. 

however,  is  the  only  part  eaten.  It  has  a  sweetish  taste.  The  scallop 
shell  was  worn  as  a  badge  by  the  crusaders,  as  evidence  of  having 
visited  the  Holy  Land. 

Pearls.  —  These  are  formed  of  nacre,  the  material  which  constitutes 
the  inner  layer  of  the  shell.  They  begin  as  deposits  around  grains  of 
sand  or  other  foreign  objects  that  have  gained  entrance  within  the  shell. 
They  are  usually  found  between  the  mantle  and  the  shell,  but  may  be 
in  almost  any  of  the  soft  parts.  It  is  said  that  the  Chinese  introduce 
little  images  into  the  cavity  of  the  pearl  oyster,  leaving  them  to  become 
coated  over  with  nacre.  The  most  valuable  pearls  are  usually  obtained 
from  the  pearl  oyster,  but  they  are  often  found  in  certain  species  of 
fresh -water  clams.  The  most  celebrated  pearl  fisheries  are  in  the 
Persian  Gulf. 

Characteristics  of  the  Bivalve  Mollusks.  —  The  clam  and 
most  of  the  other  bivalve  mollusks  have  the  following 
characteristics,  and  have  received  various  names,  accord- 
ing as  any  given  writer  places  special  emphasis  on  one 
characteristic  or  another  :  — 

1.  There  is  no  head;  hence  some  designate  the  group 
Acephala. 

2.  There  are  large,  leaflike  gills,  from  which  comes  the 
name  Lamellibranchiata. 

3.  There  is  usually  a  muscular,  tongue-shaped  or  hatchet- 
shaped  foot,  giving  rise  to  the  term  Pelecypoda. 

4.  The  mantle  consists  of  two. lobes,  each  lobe  lining 
a  valve ;  hence  they  are  called  Bivalve  Mollusks. 


CHAPTER  VIII. 


Spires 

forming 

whorl 


Sutures 


BRANCH   MOLLUSCA. 

CLASS   GASTROPODA. 

THE  gastropods  include  the  snails  and  slugs.  They  are 
of  many  kinds,  terrestrial  and  aquatic,  in  fresh  water  and  in 
salt  water,  shelled  and  shell-less,  symmetrical  and  unsym- 
metrical,  herbivorous  and  carnivorous. 

The  Shell.  —  The  shells  of  gastropods  are  usually  of  one 
piece,  therefore  they  are  often  called  univalves  in  distinc- 
tion from  the  bivalves.  Apex 
This  one-pieced  shell  is 
almost  always  in  the 
form  of  a  cone.  Some- 
times the  cone  is  nearly 
straight,  as  in  the  tooth- 
shells  ;  again  it  is  in  the 
form  of  a  very  low,  wide 
cone,  as  in  the  limpets ; 
but  in  the  great  majority 
the  cone  is  twisted  into  a 
spiral,  making  a  thick, 
short  cone  out  of  a  long 
and  slender  one.  Some- 
times this  primary  cone 
is  wound  upon  itself  to  form  a  plane  spiral  like  a  watch 
spring,  as  in  Planorbis.  But  ordinarily  the  spiral  is  an 
ascending  spiral,  which  may  be  illustrated  by  holding  the 
outer  end  of  a  watch  spring  and  pushing  the  inner  end  out 

127 


Lines  of 
growth 


-Lip 


..  Aperture 


FIG.  79.    PARTS  OF  A  SNAIL  SHELL. 


128 


Descriptive  Zoology. 


at  right  angles  to  the  plane  of  the  flat  spiral.  By  pushing 
out  the  center,  first  to  the  right  and  then  to  the  left,  we  may 
illustrate  both  the  right-handed  and  the  left-handed  shells. 
A  very  good  substitute  may  be  made  by  winding  a  narrow 
strip  of  paper  around  a  lead  pencil  at  one  end.  This, 
unwound,  forms  a  flat  spiral,  representing  the  discoid  shell. 
By  pushing  the  center,  first  to  one  side  and  then  the  other, 
illustrate  the  right-  and  left-hand  shells.  Lay  snail  shells 
alongside  a  common  wood  screw  ;  those  having  the  whorls 
run  the  same  way  as  the  threads  of  the  screw  are  right- 


Left-hand  shell  Flat  spiral  or  Right-hand  shell 

FIG.  80.    COMPARISON  OF  KINDS  OF  SNAIL  SHELLS. 

hand  shells ;  those  with  the  whorls  twisting  in  the  opposite 
direction  are  left-hand  shells. 

The  structure  and  composition  of  the  shell  are  essentially 
the  same  as  in  clams,  the  lines  of  growth  usually  showing 
plainly  parallel  to  the  border  of  the  lip. 

The  Operculum.  —  Nearly  all  sea  snails,  and  many  fresh- 
water snails,  have  a  trap  door  attached  to  the  hinder  part 
of  the  foot,  with  which  they  close  the  aperture  of  the  shell 
when  the  body  is  drawn  in.  This  covering  is  the  opercu- 


Gastropoda.  129 

lum,  and  grows  by  concentric  rings  to  keep  pace  with  the 
continually  widening  aperture. 

The  Lingual  Ribbon.  —  In  the  floor  of  the  mouth  is  a  rib- 
bon-shaped membrane  bearing  on  its  upper  surface  many 
rows  of  fine,  sharp  teeth.  This  ribbon  passes  over  a  pad  of 
cartilage,  being  pulled  forth  and  back  by  muscles.  It  acts 
like  a  rasp,  wearing  away  the  surfaces  to  which  it  is  applied. 
As  it  is  worn  away  in  front,  it  is  pushed  forward  by  a  new 
growth  behind.  In  addition  to  the  lingual  ribbon,  many 


FIG.  8 1.  FIG.  82.  FIG.  83. 

THREE  SPECIES  OF  POND  SNAILS. 

In  Figs.  82  and  83  the  aperture  is  closed  by  an  operculum. 

mollusks  of  this  group  have  also  one  or  more  jaw  plates 
in  the  mouth,  against  which  the  ribbon  works. 

The  Foot.  —  The  foot  in  the  gastropods  is  broad  and  flat. 
Resting  upon  this  wide  foot,  the  animal  creeps  or  glides, 
leaving  behind  a  slimy  trail  of  mucus,  which  is  abundantly 
secreted.  The  foot  is  symmetrical,  and  the  anterior  end  is 
more  or  less  distinctly  marked  off  as  the  head. 

The  Digestive  System.  —  The  mouth  opens  on  the  front 
or  under  surface  of  the  head.  Watch  a  snail  in  an  aqua- 
rium to  see  how  the  mouth  works.  From  the  mouth  ex- 
tends a  short  gullet,  sometimes  dilated  into  a  crop,  to  the 


i jo  Descriptive  Zoology. 

stomach,  which  in  turn  is  followed  by  the  intestine.  The 
intestine  is  usually  twisted  around  so  as  to  end  in  the 
mantle  chamber  near  the  edge  of  the  aperture  of  the  shell. 
Salivary  glands  are  almost  always  present,  and  there  is  a 
large  digestive  gland  around  the  stomach,  as  in  the  clams. 

The  Circulatory  System.  — This  is  on  essentially  the  same 
plan  as  in  clams.  The  blood  comes  from  the  gills,  or  lung, 
to  the  heart,  and  is  thence  pumped  to  the  other  parts  of  the 
body.  There  is  usually  but  one  auricle  in  place  of  two 
found  in  the  clam. 

The  Excretory  System.  —  The  gastropods  have  kidneys 
essentially  like  those  of  clams,  whose  ducts  open  into  the 
mantle  cavity.  Owing  to  the  one-sided  development,  usu- 
ally only  one  kidney  is  retained. 

The  Nervous  System.  —  The  nervous  system  is  primarily 
about  the  same  as  that  of  the  clam,  consisting  of  several 
pairs  of  ganglions  connected  by  nerve  cords.  The  twisting 
of  the  body  in  many  of  the  univalves  involves  the  nervous 
system  so  that  the  nerve  loop  becomes  twisted  into  the 
shape  of  a  figure  8. 

Sense  Organs  of  Gastropods.  —  The  eyes  of  the  snail  are 
described  below.  It  is  doubtful  how  well  a  snail  can  see, 
but  it  can  discern  light  from  darkness  and  can  perceive 
quick  movements. 

A  sense  of  touch  belongs  to  the  whole  surface  of  the 
body,  but  is  more  acute  in  the  tentacles.  At  the  base  of  the 
gills  are  organs  called  "osphradia,"  or  "smelling  patches," 
being  perhaps  organs  for  testing  the  quality  of  the  water. 
Land  snails  can  detect  odors,  arid  the  seat  of  the  sense  of 
smell  seems  to  be  in  the  tentacles. 

Respiration  in  Gastropods.  —  The  majority  of  the  gastro- 
pods breathe  by  means  of  gills.  Between  the  mantle  and 


Gastropoda.  131 

the  body,  near  the  aperture  of  the  shell,  is  a  space  called 
the  mantle  cavity.  In  this  space  lie  the  gills,  but  in  many 
cases  but  one  gill  is  developed. 

Air-breathing  Gastropods.  —  In  land  snails,  slugs,  and 
numerous  fresh-water  snails,  the  mantle  chamber  becomes 
•lore  shut  in,  leaving  a  narrow  opening,  which  is  near  the 
right  side  in  right-hand  snails,  and  on  the  left  in  the  left- 
hand  snails.  Through  this  opening,  which  is  kept  closed 
most  of  the  time,  air  is  taken  into  the  cavity,  which  acts  as  a 
lung.  The  blood  circulates  around  the  walls  of  the  lung 
cavity,  and  is  thus  brought  close  to  the  air,  so  that  an  inter- 
change can  take  place  between  the  two. 

The  Land  Snails.  —  These  are  abundant  in  damp  woods, 
especially  in  limestone  regions.  Their  shells  are  usually 
thin.  Land  snails  have  two  pairs  of  tentacles,  with  eyes  at 
the  tips  of  the  upper  or  longer  pair.  The  eyes  can  be 
pulled  in,  the  tip  disappearing  first,  as  when  in  pulling  off 
a  glove  the  tip  of  the  glove  finger  sticks  to  the  end  of  the 
finger.  If  the  tip  of  one  of  these  tentacles  is  cut  off,  it  will 
be  reproduced,  and  it  is  said  that  this  has  been  done  twenty 
times  in  succession. 

Land  snails  usually  have  no  operculums ;  but  at  the  ap- 
proach of  winter,  or  of  a  period  of  drouth,  they  bury  them- 
selves in  the  ground,  and  pull  the  body  in  until  the  foot  is 
even  with  the  edge  of  the  aperture.  A  layer  of  mucus  is 
secreted  which  completely  closes  the  aperture.  In  some 
cases  limy  material  is  added,  and,  in  any  case,  the  covering 
soon  hardens.  Sometimes  the  snail  then  withdraws  still 
farther,  and  makes  another  such  barrier,  or  even  several. 
In  the  spring,  or  at  the  return  of  moisture,  the  temporary 
door  is  cast  off,  and  the  snail  resumes  its  activity.  Snails 
have  great  vitality,  and  have  been  known  to  survive  in  this 
shut-in  condition  for  six  years  without  food. 


132  Descriptive  Zoology. 

Most  kinds  of  snails  lay  their  eggs  in  strings,  masses,  or 
clusters ;  but  the  land  snails  deposit  theirs  singly,  burying 
them  or  depositing  them  in  moist  places. 

The  French  follow  the  usage  of  the  Romans  in  eating 
the  land  snails,  and  they  are  now  imported  into  the  United 
States  .from  Europe  by  Eastern  dealers. 

In  Europe  snails  do  considerable  damage  in  gardens,  but 
they  do  not  seriously  affect  us. 

Slugs.  —  Slugs  are  air-breathing,  terrestrial  gastropods, 
almost  always  destitute  of  a  shell.  They  are  to  be  found 
in  moist  woods,  especially  under  the  bark  or  in  the  decaying 
trunks  of  fallen  trees. 

On  the  anterior  dorsal  surface  is  a  fleshy  plate,  the  mantle, 
and  near  the  right  edge  of  this  is  the  breathing  pore,  lead- 


Mamie 


FIG.  84.    SLUG. 

Near  the  lower  border  of  the  mantle  is  the  respiratory  pore. 

ing  to  the  lung.  As  in  the  land  snail,  there  are  two  pairs 
of  tentacles,  with  eyes  at  the  ends  of  the  upper  (longer) 
pair.  The  body  is  elongated  ;  but  when  the  animal  is  dis- 
turbed, it  draws  up  into  a  short,  compact  lump. 

Slugs  are  nocturnal,  hence  are  less  conspicuous  than 
snails.  They  do  considerable  damage  in  gardens,  rasping 
off  the  surfaces  of  the  leaves.  Their  presence  is  also  in- 
dicated by  the  slimy  trails  which  they  leave  behind.  One 
of  the  most  effective  ways  of  checking  them  is  to  sprinkle 
coal  ashes  over  and  around  the  plants  they  are  attacking. 


Gastropoda. 


133 


The  Pond  Snails:  —  The  pond  snails  have  the  mantle 
cavity  transformed  into  a  lung,  as  in  the  land  snails. 
They  frequently  come  to  the  surface  of  the  water  to  get 
air,  and  may  be  seen  first  to  emit  a  bubble  of  the  contained 
air,  take  a  new  supply,  and  again  descend  to  resume  their 


FIG.  85. 


FIG.  86. 


POND  SNAILS  CREEPING. 


The  largest  part  extending  from  the  shell  is  the  foot.  There  are  three  other  protruding 
organs:  (i)  the  proboscis,  in  the  center;  (2)  the  two  tentacles,  with  an  eye  at  the  base 
of  each;  (3)  outside  the  tentacles,  the  respiratory  tubes,  one  of  which  takes' in  water,  the 
other  sending  it  out.  In  Fig.  85,  the  dark  semicircle  back  of  the  shell  is  the  operculum. 

eating.  They  are  exclusively  herbivorous,  and  in  an  aqua- 
rium may  be  observed  cleaning  off  the  layer  of  green  scum, 
mostly  consisting  of  algae,  which  grows  on  the  sides  of  the 
aquarium. 


FIG.  87.    VARIATIONS  IN  A  COMMON  POND  SNAIL. 

After  Morse,  from  Packard's  Zoology. 

There  is  but  one  pair  of  tentacles,  at  the  bases  of  which 
are  the  eyes.     Only  a  few  pond  snails  have  operculums. 


134 


Descriptive  Zoology. 


The  eggs  are  laid  in  clusters,  usually  enveloped  in  a  gelat- 
inous mass ;  and  in  an  aquarium  are  usually  deposited  on 
the  side  of  the  glass  in  a  very  favorable  place  for  watching 
their  development.  There  are  three  common  genera,— 
Limnea,  a  right-hand  shell ;  Planorbis,  a  discoid  shell,  or 
flat  spiral ;  and  Physa,  a  left-hand  spiral  (Fig.  80). 

The  River  Snails.  —  These  are  not  entirely  distinct  from 
the  pond  snails ;  still,  they  nearly  all  breathe  by  means 
of  gills,  and  most  of  them  have  operculums.  Being  gill 
breathers,  they  of  course  do  not  come  to  the  surface  to 
breathe,  hence  are  not  usually  so  conspicuous.  Some  of 
them  have  a  projecting  tube  on  each  side  of  the  neck, 
the  water  entering  through  one  of  the  tubes  to  the  gill,  and 
passing  out  through  the  other.  The  eyes  are  like  those  of 

the  pond  snails  in  being 
borne  at  the  bases  of  the  one 
pair  of  tentacles.  In  some 
of  the  river  snails  the  young 
are  brought  forth  alive. 

Sea  Snails.  —  These  are 
found  chiefly  along  the 
shore,  not  often  in  very  deep 
water.  They  are  numerous 
in  kinds  and  individuals,  and 
vary  greatly  in  both  color 
and  form.  In  size  they  vary 
from  almost  microscopic  to 
a  foot  and  a  half  or  more 
in  length.  They  also  vary 
greatly  in  shape,  from  globu- 
lar (Fig.  88)  to  slender  tapering  forms  resembling  screws. 
The  shell  is  usually  right-handed,  and  the  majority  have 
operculums.  Nearly  all  breathe  by  means  of  gills. 


FIG.  88.    A  LARGE  SEA  SNAIL 
(NATICA). 

It  feeds  on  clams,  etc.,  boring  through 
their  shells. 


Gastropoda. 


'35 


A  Drilling  Sea  Snail.  — Natica  (see  Fig.  88)  is  common  on  the  New 
England  coast.  It  is  one  of  the  largest  of  the  snails  found  along  the 
northern  shores,  sometimes  reaching  a  length  of  five  inches.  Natica  is 
carnivorous,  and  lives  mostly  on  clams  and  other  bivalves.  It  burrows 
in  the  mud  or  sand  ;  and  when  it  finds  a  clam,  it  uses  the  lingual  riobon 
and  bores  a  hole  through  the  shell,  rotating  its  own  body  meanwhile. 


Tentacles 


Gills 


FIG.  89.    A  SEA  SNAIL  (NATICA)  CRAWLING. 

Showing  the  very  large  foot  "(surrounding  the  shell). 

It  produces  as  neat  a  countersunk  hole  as  any  made  by  a  drill  for  the 
head  of  a  screw  such  as  may  be  seen  in  any  door  hinge.  After  the  hole 
is  made  through  the  shell,  the  soft  body  of  the  clam  is  eaten. 

Sea  Slugs.  —  Sea  slugs  are  found  near  shore,  on  rocks  or  among 
seaweeds.  Many  of  them  are  devoid  of  shells  when  adult,  but  all.  have 
shells  in  their  earlier  stages.  Many  of  them  are  symmetrical  externally, 
but  few  are  so  in  their  internal  structure,  —  the  intestine,  for  example, 
usually  ending  on  the  right  side.  In  some  the  gills  are  covered,  in  others 
exposed.  The  gills  often  project 
as  leaflike  appendages  on  the 
posterior  part  of  the  dorsal  sur- 
face ;  and  the  whole  animal,  in 
form  and  color,  has  such  a  close 
resemblance  to  the  seaweeds,  on 
which  it  crawls  and  feeds,  that  it 
escapes  the  enemies  to  which,  in 
its  defenseless  condition,  it  would 
be  an  easy  prey.  Some  of  the 

sea  slugs  can  swim,  and  usually  do  so  inverted,  with  the  flat  surface  of 
the  foot  at  the  surface  of  the  water.  When  the  adult  has  a  shell,  it 
sometimes  has  its  edges  covered  by  the  overlapping  mantle,  and  some- 
times is  completely  inclosed  by  a  sac  like  mantle. 


FIG.  90.    NAKED  MOLLUSK. 

From  Kingsley's  Comparative  Zoology. 


136  Descriptive  Zoology. 

Limpets. — Along  the  shore  there  are  to  be  found  gastro- 
pods with  low  conical  shells,  clinging  close  to  the  surface 
of  the  rocks.  They  may  be  scraped  off  by  a  quick  motion 
with  a  dull  knife,  but  if  they  are  first  alarmed  they  draw  down 
and  adhere  so  firmly  to  the  rock  that  one  is  likely  to  break 
the  shell  in  the  attempt  to  dislodge  them.  The  keyhole 
limpet  is  so  named  from  the  shape  of  the  hole  at  the  apex. 

The  Ear-shell  or  Abalone.  — Closely  related  to  the  limpets 
is  the  "  ear-shell "  found  on  the  California  coast.  There  is 


FIG.  92.    ABALONE  OR  EAR-SHELL. 

Furnishes  mother-of  pearl  for  inlaid  work. 


FIG.  91.    LIMPET. 

Surface  view  and  side  view.  FlG.  93.     RED  CHITON  (kl'tSn). 

a  row  of  perforations  near  one  margin  of  the  shell,  through 
which  tentacles  project.  The  interior  of  the  shell  is  pearly 
and  of  beautifully  variegated  color.  It  is  known  as  "  aba- 
lone,"  and  is  much  used  for  inlaid  work. 

A  Multivalved  Mollusk.  —  Chiton  is  a  very  peculiar 
marine  mollusk.  It  is  low  and  flat,  creeping  like  the  lim- 
pets. But  the  shell  consists  of  a  series  of  eight  pieces  over- 
lapping one  another  from  the  anterior  to  the  posterior  end. 
The  animal  is  completely  symmetrical,  both  internally  and 
externally  (Fig.  93). 


Gastropoda.  137 

CHARACTERISTICS  OF  THE  GASTROPODA. 

1.  The  gastropods  have  a  foot  which  is  developed  as  a 
broad,  flat,  creeping  disk. 

2.  There  is  usually  a  well-developed  bead,  with  eyes  and 
tentacles. 

3.  The  majority  have  a  univalve  shell,  but  this  is  some- 
times lacking. 

4.  Body  often  unsymmetrical. 

5.  There  is  a  lingual  ribbon. 


CHAPTER    IX. 
BRANCH   MOLLUSCA. 

CLASS   CEPHALOPODA. 

THE  cephalopods  include  such  forms  as  the  squid, 
cuttlefish,  and  chambered  nautilus. 

The  Squid.  —  The  squid  is  the  best  example  of  the  group. 
It  is  abundant  along  the  Atlantic  coast.  Squids  swim  in 
schools,  and  are  frequently  found  following  schools  of 
young  herring  and  mackerel,  on  which  they  feed.  They 


FIG.  94.    COMMON  SQUID. 

From  Packard's  Zoology. 

are  chiefly  nocturnal,  though  not  infrequently  seen  in  the 
daytime.  After  a  storm  the  writer  has  seen  the  beaches 
on  Cape  Ann  covered  with  them  in  the  morning,  where 
they  have  been  left  stranded  by  the  receding  tide. 

The  Form  of  the  Squid.  —  Seen  from  above  the  body  ap- 
pears cylindrical.     At  the  anterior  end  is  a  well-developed 


Cephalopoda.  139 

head  and  a  distinct  neck.  At  the  tail  end  are  two  triangu- 
lar fins  which  together  present  the  appearance  of  a  dia- 
mond-shaped arrow  point.  Seen  from  below  the  body  is 
conical  or  fusiform,  ending  in  a  distinct  point  behind,  the 
tail  fin  covering  about  one  third  of  the  body.  The  fins  are 
attached  at  the  sides  of  the  dorsal  part  of  the  hinder  part 
of  the  body,  and  can  be  wrapped  more  or  less  around  the 
tapering  posterior  end.  The  common  kinds  of  squids  sel- 
dom attain  a  length  of  a  foot. 

The  Head.  —  From  the  front  of  the  head  project  five 
pairs  of  arms,  arranged  in  a  circle  around  the  mouth. 
Four  pairs  of  these  arms  are  short,  and  taper  to  a  point. 
One  pair  are  much  longer,  being  nearly  as  long  as  the  body, 
and  are  enlarged  near  the  ends.  On  the  inner  surfaces  of 
the  short  arms,  and  on  one  side  of  the  club-shaped  end  of 
the  long  arms,  are  rows  of  suckers.  These  are  button- 
shaped  or  saucer-shaped  bodies,  attached  to  the  arms  by 
stalks.  The  outer  surface  is  hollow,  and  when  applied  to 
any  surface  the  center  can  be  retracted  by  the  muscular 
stem  by  which  it  is  attached,  thus  making  a  strong  hold- 
fast. The  long  arms  are  sometimes  called  the  "grasping 
arms." 

On  the  sides  of  the  head  are  the  two  large  eyes,  the 
most  highly  developed  eyes  among  the  invertebrates. 

The  Mantle.  — There  is  an  opening  all  around  the  neck 
where  it  projects  from  the  mantle  cavity.  The  whole 
external  envelope  of  the  body  is  the  mantle,  inside  which 
is  the  conical  body,  with  a  space  extending  nearly  all  around 
it  except  along  the  dorsal  line,  where  the  outside  of  the 
body  mass  is  attached  to  the  inside  of  the  mantle.  The 
mantle  is  muscular  and  very  powerful. 

The  Pen.  —  The  squid  has  no  external  shell,  and  the 
only  representative  of  one  is  a  horny  structure,  somewhat 


140  Descriptive  Zoology. 

similar  in  shape  to  a  feather.  This  is  imbedded  in  the  dor- 
sal part  of  the  mantle,  extending  nearly  the  whole  length  of 
the  back.  It  is  wholly  inclosed  in  a  capsule  in  the  thick- 
ness of  the  mantle  wall. 

The  Siphon  or  Funnel.  —  Projecting  from  the  mantle 
cavity  under  the  head  is  a  funnel  whose  narrow  end  opens 
forward  and  whose  wide  end  points  back  into  the  mantle 
cavity. 

How  the  Squid  Swims. —  Water  is  taken  into  the  mantle 
cavity  through  the  open  space  around  the  neck.  Then 
the  edge  of  the  mantle  is  contracted  and  is  fastened  to  th<5 
neck  and  sides  of  the  base  of  the  funnel  by  a  set  of  ca~- 
tilages  that  have  a  sort  of  "  hook  and  eye  "  arrangement. 
Then  by  the  contraction  of  the  mantle  the  water  is  forced 
out  through  the  siphon,  and  by  reaction  the  squid  is  rapidly 
driven  backward  through  the  water.  So  swift  is  its  move- 
ment that  it  has  received  the  popular  name  of  "  arrow  fish." 
Squids  sometimes  dart  clear  out  of  the  water,  and,  when 
kept  in  aquariums,  thus  jump  over  the  sides.  Their  mo- 
tion is  amazing,  not  only  on  account  of  its  swiftness,  but 
because  there  is  no  manifest  cause  of  the  motion.  They 
propel  themselves  by  the  outgush  of  water,  which  is  in- 
visible, and  the  change  in  size  from  the  contraction  of  the 
mantle  is  so  slight  as  to  be  unnoticed.  To  the  uninstructed 
it  is  as  inexplicable  as  the  motion  of  a  trolley  car  is  to 
a  savage.  When  the  squid  wishes  to  move  slightly,  it 
does  so  by  gently  flapping  the  tail  fins. 

The  Ink  Bag.  —  The  squid  has  an  ink  bag,  which  lies 
near  the  rectum,  and  which  opens  near  the  anal  opening, 
near  the  inner  end  of  the  funnel.  When  in  flight  from  a 
pursuing  fish,  a  discharge  of  ink  is  sent  out  in  the  strong 
gush  of  water  through  the  siphon.  This  makes  a  dark 
cloud  in  the  water,  under  cover  of  which  the  chances  of 


Cephalopoda.  141 

escape  are  greatly  increased.  This  ink  is  the  original 
"sepia"  used  as  ink  by  the  Chinese  and  Japanese.  Some 
of  this  ink,  from  the  fossil  squid,  has  been  used  to  make  a 
drawing  of  the  animal  from  which  the  ink  was  taken. 

The  Color  of  the  Squid.  —  Ordinarily  the  dead  squid  is 
of  a  pale  color,  tinted  with  purplish.  In  the  living  animal 
the  color  is  very  changeable,  passing  quickly  from  red  to 
blue  or  purple,  and  one  part  may  have  one  of  these  colors 
while  other  parts  have  another  color.  This  change  of  color 
is  due  to  several  different  sets  of  colored  cells,  called  "chro- 
matophores " ;  these  expand  and  relax  under  the  control 
of  muscles,  which  are  in  turn  governed  by  nerves.  The 
color  changes  in  quick  flashes,  exceeding  the  quickness  of 
blushing  and  pallor  observed  in  the  human  face.  This 
change  of  color  is  undoubtedly  for  the  sake  of  protection, 
though  one  is  inclined  to  wonder  why  such  intense  hues 
should  be  employed.  As  a  school  of  squids  are  swimming 
along  they  are  often  seen  to  change  their  color  abruptly, 
according  to  the  bottom  over  which  they  are  passing. 

Methods  of  Escape  from  Enemies.  —  (i)  The  squid  may 
elude  observation  by  taking  on  the  color  of  its  surround- 
ings. (2)  By  speedy  flight.  (3)  In  flight  its  chances  of 
escape  are  increased  by  the  discharge  of  ink,  which  makes 
the  water  turbid. 

The  Digestive  System.  — The  brown  beak  projects  from 
the  center  of  the  circle  of  arms  in  front  of  the  head.  It 
consists  of  a  pair  of  hard,  horny  jaws,  somewhat  resem- 
bling the  beak  of  a  parrot,  except  that  the  upper  jaw 
is  much  smaller  than  the  lower,  into  which  it  shuts. 
In  addition  to  the  beak  there  is  a  lingual  ribbon,  as  in  the 
snails.  From  the  mouth  extends  a  long,  narrow  gullet. 
Well  back  in  the  body  is  the  muscular  stomach,  which 
has  a  large  cecum.  The  intestine  then  extends  forward, 


142  Descriptive  Zoology. 

ending  in  the  mantle  cavity  near  the  large  inner  end  of 
the  funnel.  The  excrement,  as  in  the  clam,  is  swept  out 
by  the  water  current.  There  are  salivary  glands  ;  and  a 
large  digestive  gland,  often  called  the  "liver,"  pours  its 
secretion  into  the  cecum. 

How  the  Squid  captures  its  Prey.  —  The  squid  is  a 
voracious  animal  and  lives  largely  on  small  fishes.  It 
sometimes  stealthily  approaches  a  fish  by  almost  imper- 
ceptible motions  of  its  fins,  until  it  is  within  grasping  dis- 
tance, when  it  suddenly  seizes  the  fish  and  quickly  kills  it 
by  biting  it  in  the  back  of  the  neck.  Again  it  swims 
swiftly,  and  suddenly  darts  among  a  school  of  fishes,  and 
turns  and  kills  its  prey  by  a  quick  snap  of  its  powerful 
jaws.  It  also  eats  crabs  and  other  animals.  While  it  is 
pursuing  the  smaller  fishes,  it  may,  in  turn,  be  chased  by 
larger  fishes. 

Respiration  and  Circulation  in  the  Squid. — The  squid 
has  two  plumelike  gills  attached  to  the  under  surface  of 
tne  body,  extending  along  the.  mantle  cavity.  The  circu- 
latory system  is  more  highly  developed  than  in  any  of 
the  other  mollusks. 

The  Nervous  System.  —  The  nervous  system,  too,  is 
highly  developed  and  concentrated,  consisting  of  several 
pairs  of  ganglions  in  the  head,  forming  a  central  brain, 
from  which  nerves  extend  to  the  other  parts  of  the  body. 
There  is  a  protecting  case  of  cartilage,  a  rudimentary  cra- 
nium, supporting  and  partly  surrounding  the  brain. 

The  Senses  of  the  Squid.  —  The  eyes  are  highly  devel- 
oped, and  evidently  have  keen  sense  of  sight.  A  number 
of  squids  may  be  lying  side  by  side  in  the  water,  perfectly 
motionless,  perhaps  relying  on  their  quietness  and  protec- 
tive color.  A  sudden  motion  on  the  part  of  a  person  ob- 


Cephalopoda. 


143 


serving  them  may  cause  them  to  dart  off  like  so  many  arrows. 
There  is  a  rudimentary  ear.  Some  authors  say  that  the  squid 
has  the  five  senses  which  are  best  known  in  our  bodies. 

The  Squid  used  as  Bait.  —  Squids  are  used  very  extensively  as  bait 
in  the  cod  fishery,  a  single  small  vessel  sometimes  using  eighty  thou- 
sand in  six  weeks.  They  are  caught  mainly  by  means  of  nets.  They 
are  either  kept  fresh  for  this  use,  or  may  be  " pickled"  in  brine. 
They  are  also  used  in  fishing  for  bluefish. 


FIG.  95.    OCTOPUS,  FROM  BRAZIL. 

From  Packard's  Zoology. 

Giant  Squids.  —  Some  species  of  squids  have  a  body  over  nine  feet 
long,  with  arms  thirty  feet  in  length.  Some  of  these  may  have  given 
rise  to  the  stories  of  "sea  serpents." 

The  Octopus.  — As  the  name  indicates,  these  forms  have  eight  arms 
instead  of  ten,  as  in  the  squids  and  cuttles.  The  body  is  short  and 
nearly  spherical.  Though  the  octopus  can  swim,  it  is  very  much  less 
active  than  the  preceding  forms,  spending  most  of  the  time  crawling 
over  the  bottom,  resting  on  the  basis  of  the  circle  of  arms  with  the  body 
held  above.  The  arms  are  more  or  less  connected  by  webs  at  the  base. 
There  is  neither  internal  nor  external  shell.  A  Pacific  coast  octopus  has 
body  a  foot  long,  the  arms  having  a  radial  spread  of  twenty-eight  feet. 


144  Descriptive  Zoology. 

Many  weird  tales  are  told  of  the  octopus,  most  of  which  have  little  or  no 
foundation.  In  fact,  there  is  no  satisfactory  evidence  that  an  octopus 
ever  intentionally  attacked  a  human  being.  In  countries  adjacent  to 
the  Mediterranean  the  octopus  is  largely  used  as  food. 

The  Nautilus.  —  The  nautilus  is  closely  related  to  the  squids  and 
cuttlefishes,  but  has  the  body  inclosed  in  a  flat-spiral  shell.  From 
time  to  time  the  animal  moves  forward  and  partitions  off  the  space  in 
the  shell  which  it  formerly  occupied,  the  live  animal  occupying  only  the 


FIG.  96.    CHAMBERED  NAUTILUS. 

Showing  chambers  with  soft  body  in  outer  chamber. 

From  Packard's  Zoology. 

outermost  space  in  the  shell.  It  retains  its  hold  on  the  smallest  and 
oldest  portion  of  the  shell,  however,  by  means  of  a  slender  fleshy  cord 
which  passes  through  a  series  of  holes  left  in  the  partitions.  The  inner, 
abandoned  spaces  are  filled  with  gas.  From  this  fact  of  growth  the 
animal  is  commonly  called  the  chambered  nautilus,  though  it  is  also 
called  the  pearly  nautilus,  from  the  pearly  lining.  It  lives  in  the 
South  Seas. 

Fossil  Chambered  Shells.  —  While  the  nautilus  is  almost  the  only 
living  form  of  this  peculiar  plan  of  growth,  there  are  many  fossil  cham- 
bered shells.  Two  of  the  most  noteworthy  of  these  are  the  Ammon- 


Cephalopoda.  145 

ites,  a  spiral  form  very  similar  to  the  nautilus,  and  a  perfectly  straight 
conical  shell,  hence  named  Orthoceras. 

The  Cuttlefish.  —  In  the  cuttlefish  the  lateral  fins  extend  along 
the  whole  of  the  length  of  the  side,  and  the  body  is  less  sharply 
conical.  Though  essentially  like  the  squid,  they  are  less  swift  in  their 
flight.  In  the  sharp  prow  of  the  squid  one  sees  the  build  of  a  racing 
shell,  while  the  greater  width  of  the  cuttlefish  suggests  the  increased 
breadth  of  beam  in  an  ordinary  rowboat.  Cuttlefishes  feed  on  crabs, 
clams,  and  fishes.  The  internal  shell  of  the  cuttlefish  is  calcareous, 
instead  of  horny  as  in  the  squid,  and  is  well  known  from  its  use  in  fur- 
nishing limy  material  to  canary  birds.  The  ink  of  the  cuttlefish  is  the 
basis  of  the  pigment  sepia.  Cuttlefishes  live  near  shore  and  are  used 
extensively  as  food  (in  the  Old  World)  as  well  as  for  the  ink  and 
cuttle  bone. 

CHARACTERISTICS   OF   THE   CEPHALOPODA. 

1.  There  is  a  distinct  head  with  highly  developed  eyes. 

2.  The  foot  has  developed  around  the  head  (hence  the 
name  Cephalopoda),  and  is  divided  into  a  number  of  arms. 

3.  Part  of  the  foot  develops  into  a  funnel-like  siphon. 

4.  The  shell  may  be  external,  internal,  or  lacking. 

5.  Chromatophores  are  found  in  the  skin. 

6.  There  is  a  beak  and  a  lingual  ribbon. 

CHARACTERISTICS   OF   THE   MOLLUSKS. 

There  is  such  a  great  diversity  among  the  mollusks  that 
it  is  very  difficult  to  make  any  concise  statement  of  their 
common  characteristics.  Some  have  shells,  others  none ; 
some  are  aquatic,  others  terrestrial ;  some  live  in  fresh 
water,  others  in  the  sea ;  some  breathe  by  gills,  others  by 
lungs ;  some  are  herbivorous,  some  carnivorous ;  some  are 
free,  others  sessile;  the  limpet,  though  free,  practically  is 
glued  to  its  place  on  a  rock ;  the  slug  is  so  slow  that  we 
have  borrowed  his  name  to  make  a  common  adjective, 


146  Descriptive  Zoology. 

while  the  scallop  swims  actively ;  clams  and  oysters  feed 
on  microscopic  forms  swept  in  by  currents  of  water,  while 
the  cephalopods  prey  upon  the  most  active  fishes ;  there  is 
strong  contrast  between  the  monotonous  existence-  of  the 
headless  clam,  burrowing  in  the  mud,  and  the  free  life  of 
the  cuttlefish,  with  its  distinct  head  and  highly  developed 
eyes ;  the  oyster  is  fixed  to  his  spot,  almost  as  passive  as  a 
sponge,  while  the  squid  darts  so  swiftly  that  it  is  called 
the  arrow  fish. 

Nevertheless  the  following  characteristics  belong  in 
common  to  the  various  classes  of  mollusks :  — 

1.  Aside  from  the  shell  the   body  is  soft;  hence  the 
name  "mollusk,"  soft. 

2.  The  body  is  unsegmented,   in   distinction  from   the 
arthropods,  the  vertebrates,  and  many  worms. 

3.-  There  is  an  extension  of  the  skin  called  the  "  mantle," 
which  usually  produces  a  shell,  univalve,  bivalve,  or  rarely 
multivalve. 

4.  There  is  usually  a  ventral  muscular  extension,  the 
foot,  which,  in  most  forms,  serves  in  locomotion. 

5.  They  are  mostly  bilaterally  symmetrical,  but  some 
are  much  distorted. 

6.  The  nervous  system  consists  of  about  three  pairs  of 
ganglions,  connected  by  nerve  cords. 

CLASSIFICATION   OF   THE   MOLLUSCA. 

As  all  earlier  classifications  are  based  on  superficial 
characteristics,  it  was  to  be  expected  that  the  first  classifi- 
cations of  mollusks  would  be  by  their  shells.  Hence  the 
science  of  Conchology.  But  now  we  class  the  mollusks, 
as  other  groups,  by  their  general  plan  of  structure, 
mainly  of  the  soft  parts,  for  these  parts  make  the  shell, 
and  the  shell  does  not  mould  them. 


Cephalopoda.  147 

They  have  been  classed  according  to  the  head  into 
Acephala  (headless,  clams),  Cephalophora  (head-bearing, 
snails),  and  Cephalopoda  (head-footed,  squids). 

The  classification  here  adopted  is  based  on  the  foot  and 
presents  three  chief  classes  :  — 

1.  Pelecypoda  (hatchet-footed) ;  example,  the  clam. 

2.  Gastropoda  (stomach-footed) ;  example,  the  snail. 

3.  Cephalopoda  (head-footed);  example,  the  squid. 


CHAPTER   X. 
BRANCH   CHORDATA. 

THIS  branch  is  mainly  composed  of  the  vertebrates,  or 
backboned  animals,  that  is,  fishes,  amphibians, reptiles,  birds, 
and  mammals.  But  it  is  now  found  necessary  to  class  with 
them  certain  other  animals  formerly  regarded  as  inverte- 
brates. Hence  the  old  branch  Vertebrata  is  made  a  sub- 
branch,  and,  with  two  other  subbranches,  included  in  the 
branch  Chordata.  The  chordate  animals  are  characterized 
by  the  possession  of  a  dorsal  chord  or  notochord.  This  is 
a  supporting  rod  extending  along  the  dorsal  region  between 
the  body  cavity  and  the  main  nervous  system  or  spinal 
cord.  While  the  notochord  is  always  present  in  the  young, 
it  is,  with  a  few  exceptions,  replaced  in  the  adult  by  a  seg- 
mented cartilaginous  or  bony  axis,  which  is  known  as  the 
spinal  or  vertebral  column.  In  other  words,  the  notochord 
is  a  sort  of  forerunner  of  the  backbone. 

Subdivisions  of  Chordata.  —  The  branch  Chordata  is 
divided  into  three  subbranches  :  — 

1 .  Adelochorda,  wormlike,  marine  forms  (Balanoglossus). 

2.  .Urochorda,  the  tunicates  or  ascidians. 

3.  Vertebrata,  lancelet  to  mammals. 

Division  A.  —  Acrania,  the  lancelets. 

(a)  Cyclostomata,  without 
jaws  (lampreys). 


Division  B.  —  Craniata. 


(b)  Gnathostomata,    with 


jaws  (true  fishes  to 
mammals). 

148 


Chordata.  149 

SUBBRANCH   UROCHORDA. 

As  an  example  of  the  urochordates  we  may  take  the 
common  ascidian.  Such  forms  are  sometimes  called  "sea 
peaches"  or  "sea  pears,"  indicating  the  size,  shape,  and 
general  appearance.  They  are  attached  by  one  end  to 
rocks  or  shells  or  even  to  a  muddy  bottom.  There  are  two 
holes,  one  at,  and  the  other  near,  the  free  end.  When  the 
living  animal  is  disturbed,  it  ejects  water  from  both  of 
these  holes,  hence  the  more  common  name,  "sea  squirt." 
The  tough  muscular  external  coat,  or  tunic,  also  gives  the 
name  tunicata.  They  are  all  marine. 

Structure  of  an  Ascidian.  —  Inside  the  outer  wall,  or  tunic, 
is  a  lining,  the  pharynx,  which  hangs  free  below  its  attach- 
ment near  the  larger  opening,  the  mouth.  The  pharynx 
is  perforated  by  many  small  apertures  through  which  water 
is  driven  by  cilia.  From  the  space  around  the  pharynx, 
the  peribranchial  chamber,  the  water  passes  out  through  the 
second,  or  exhalant,  aperture.  From  the  lower  end  of 
the  pharynx  arises  the  gullet,  which  soon  enlarges  into  the 
stomach.  A  relatively  short  intestine  empties  into  the 
peribranchial  chamber,  where  the  outgoing  water  current 
catches,  the  refuse  of  digestion.  There  is  a  simple  tubular 
heart,  which  is  unique  in  its  action.  After  pumping  the 
blood  in  one  direction  for  a  few  beats,  it  reverses  its  action 
and  sends  the  blood  the  other  way.  The  nervous  system 
is  very  simple,  consisting  mainly  of  a  ganglion  between 
the  two  apertures  (see  Fig.  97). 

Development  of  Ascidians.  —  In  the  above  account  of  the 
structure  of  an  ascidian  there  is  no  trace  of  relationship  to 
the  other  chordates,  and  so  long  as  the  structure  of  the 
adult  only  was  known,  no  one  even  guessed  at  its  real 
affinities.  But  the  study  of  its  development  threw  light  on 


150  Descriptive  Zoology. 

the  subject.  It  was  found  that  the  larval  ascidian  possesses 
a  long  tail  in  which  is  a  distinct  notochord  and  an  elongated 
nerve  cord.  But  early  in  life  the  larva  attaches  itself  by 
its  head,  the  tail  gradually  disappears,  and  the  elongated 
nerve  cord  becomes  shortened  to  a  mere  ganglion.  In  the 


Mouth 

Nervous 
system 


Water  exit 


Heart 


FIG.  97.    DIAGRAM  OF  A  TUNICATE  OR  ASCIDIAN  (SEA  SQUIRT). 

From  Kingsley's  Zoology. 

sessile  adult  animal  no  trace  remains  of  the  primitive  noto- 
chord. This  illustrates  what  is  called  "  retrograde  devel- 
opment " ;  or,  in  simple  words,  the  ascidian  is  a  degenerate 
chordate,  perhaps  even  a  degenerate  vertebrate.  This  is 
one  instance  of  degeneration  in  which  the  real  relationship 
is  indicated  by  the  structure  of  the  young  rather  than  by 
that  of  the  adult. 


Acrania.  151 

Other  Tunicates.  —  Some  tunicates  are  minute  and  free- 
swimming  by  means  of  a  vibratile  tail.  Other  small  forms 
are  barrel-shaped,  and  exhibit  a  marked  "  alternation  of 
generations."  Many  of  the  tunicates  live  and  multiply  by 
budding  in  colonies. 

SUBBRANCH  VERTEBRATA. 

The  Lowest  Vertebrate. — To  the  beginner  it  would  seem 
easy  to  determine  whether  or  not  an  animal  has  a  back- 
bone, and  so  to  decide  whether  it  is  a  vertebrate  or  an 
invertebrate.  But  let  us  take  a  glance  at  what  is  by  many 
authors  regarded  as  the  simplest  of  the  vertebrates. 

The  Lancelet.  —  The  lancelet  (Branchiostoma,  or  Amphi- 
oxus)  is  fishlike  in  form  and  general  appearance,  only  two 


FIG.  98.    DIAGRAM  OF  LANCELET. 

Above  (dotted)  is  the  nervous  system;  below  it  (cross-lined)  the  notochord;  the  mouth  is  sur- 
rounded by  a  circle-  of  tentacles;  below  the  notochord  is  a  row  of  gill  slits;  the  vent  is 

near  the  posterior  (right)  end  below.     From  Kingsley's  Zoology. 

« 

or  three  inches  long,  and  nearly  transparent.  It  is  marine, 
being  found  in  warm  waters.  Specimens  are  taken  along 
the  south  Atlantic  coast.  The  lancelet  has  a  notochord 
extending  to  the  anterior  end,  or  the  snout.  There  is  a 
nerve  cord  along  the  dorsal  side  of  the  notochord,  but  the 
anterior  end  is  hardly  well  enough  developed  to  deserve 
being  called  a  brain.  It  has  blood  tubes,  but  no  heart. 
There  is  a  tail  fin,  but  no  limbs,  not  even  paired  fins.  The 
mouth  is  surrounded  by  a  circle  of  fringelike  tentacles. 
Back  of  the  mouth  extends  the  capacious  pharynx,  whose 
walls  are  perforated  by  numerous  ciliated  gill  slits.  At  the 


152  Descriptive  Zoology. 

posterior  end  of  the  pharynx  the  intestine  continues  to  the 
anus,  situated  posteriorly  and  ventrally.  By  the  action  of 
the  cilia  water  is  taken  into  the  mouth,  passes  through  the 
slits  in  the  wall  of  the  pharynx,  and  enters  a  space  around 
the  pharynx,  called  the  atrial  or  peribranchial  chamber, 
whence  it  escapes  to  the  exterior  through  a  ventral  opening 
called  the  atrial  pore.  The  lancelet  usually  lies  buried 
in  the  sand,  with  only  the  mouth  projecting.  It  gets  both 
food  and  oxygen  from  the  water,  which  is  circulated 
through  the  body  by  means  of  ciliary  action.  The  lancelet 
occasionally  swims  by  fishlike  movements. 

Classification  of  the  Lancelet.  —  It  might,  at  first  thought, 
seem  strange  that  so  simple  an  animal  should  be  classed 
with  a  group  having  such  complex  structure  as  the  verte- 
brates. The  lancelet  has,  in  fact,  been  placed  with  the 
mollusks,  and  later  with  the  fishes,  but  is  now  located  at 
the  foot  of  the  vertebrate  series,  chiefly  on  account  of  the 
possession  of  the  notochord  and  the  dorsal  nervous  system. 
It  is  really  hard  to  locate  an  animal  with  colorless  blood, 
and  with  neither  skull,  brain,  heart,  auditory  organs,  paired 
eyes,  nor  paired  fins. 

The  student  who  gets  his  ideas  of  classification  almost 
entirely  from  reading  is  apt  to  think  that  the  animal  king- 
dom is  divided  into  groups  separated  by  clear  and  distinct 
dividing  lines.  But  when  he  undertakes  the  actual  exami- 
nation of  any  considerable  series  of  animals,  he  often  finds 
that  two  groups,  which  he  regarded  as  distinct,  actually 
merge  one  into  the  other  so  gradually  that  he  finds  it  diffi- 
cult to  see  just  where  the  line  of  division  should  be  drawn. 
The  line  of  demarcation  must  frequently  be  so  drawn  that 
it  cuts  across  some  intermediate  forms,  part  of  whose  char- 
acteristics lie  on  one  side  and  part  on  the  other.  In  some 
cases  the  intermediate  forms  are  living ;  in  other  cases  the 


Cyclostomata.  153 

"connecting  links"  are  represented  only  by  fossil  forms, 
as,  for  example,  the  extinct  animals  that  connect  the 
reptiles  and  the  birds. 

The  lancelets  are  plainly  on  the  threshold  of  the  verte- 
brate household.  By  some  authorities  they  are  denied 
admittance,  and  must  wait  just  outside.  Others  allow 
them  barely  to  cross  the  threshold  and  humbly  take  their 
place  by  the  door,  the  lowest  of  the  great  branch  at  whose 
head  stands  man. 

Distinction  of  the  Lancelet  from  Other  Vertebrates.  —  On 
account  of  the  poorly  developed  brain  and  the  absence  of 
a  cranium,  the  lancelet  is  placed  by  itself  in  a  division 
called  Acrania,  while  all  the  other  vertebrates  are  desig- 
nated as  Craniata,  from  the  presence  of  a  skull  and  the 
higher  development  of  the  brain. 

CLASS   CYCLOSTOMATA. 

The  lowest  of  the  craniate  vertebrates  are  the  Cyclo- 
stomata. This  class  includes  the  lampreys,  or  lamprey 
eels,  as  they  are  often  called,  and  the  hagfishes.  They 
are  eel-like  in  form,  without  scales,  and  with  smooth,  slimy 
skins.  They  have  no  jaws,  but  a  round,  sucking  mouth, 
hence  they  are  sometimes  called  the  "  round-mouthed  eels." 
There  is  a  single  nostril  on  top  of  the  head.  They  have 
dorsal  and  caudal  fins,  but  no  paired  fins.  There  are  sev- 
eral pairs  of  purse-shaped  gills,  hence  they  are  called  by 
some  authors  Marsipobranchii.  The  skeleton  has  no  trace 
•of  bone,  being  wholly  cartilaginous  and  very  imperfectly 
developed.  The  internal  organs  are,  in  many  features, 
similar  to  those  of  the  true  fishes. 

Lampreys  are  rather  widely  distributed.  They  are 
found  along  the  Atlantic  coast  and  ascend  the  rivers. 


Descriptive  Zoology. 


Some  appear  to  live  permanently  in  our  large  lakes.    "By 
their   sucking   mouths .  they  attach  themselves  to  fishes, 


FIG.  99.    LAMPREY  EEL. 

After  Goode.  -<•  From  Kingsley's  Zoology. 

sucking  their  blood,  or  even  penetrating  their  bodies. 
They  are  the  only  vertebrates  known  to  live  a. parasitic 
life.  In  Europe  the  sea  lampreys  are  valued  as  food. 

CLASS  PISCES. 
Example.  — The  Ringed  Perch. 

Life  of  a  Perch.  —  If  one  stops  to  consider  what  are  the 
chief  objects  in  life  with  a  fish,  he  soon  sees  that  it  is  well 
expressed  in  the  words  "  to  eat  and  not  be  eaten." 


ANAL  FIN 


FIG.  ioo.    EXTERNAL  FEATURES  OF  A  PERCH. 

In  order  to  secure  food  and  escape  enemies  the  fish 
must  have  sense  organs  and  organs  of  locomotion. 


Pisces.  155 

How  the  Fish  Floats.  —  Before  taking  up  the  question  of 
locomotion  in  fishes,  let  us  first  consider  how  it  is  that  the 
fish  can  keep  its  place  in  the  water  without  effort,  neither 
rising  nor  sinking.  A  freshly  killed  fish  usually  sinks, 
showing  that  its  body  is  slightly  heavier  than  water. 
Almost  every  one  knows  that  after  a  fish  has  been  dead 
a  short  time  it  usually  floats  (commonly  with  the  ventral 
surface  upward).  This  is  due  to  the  development  of  gases 
in  the  intestines. 

Most  fishes  have  air  bladders  (or  swim  bladders),  by 
means  of  which  they  can  regulate  their  position  in  water. 
By  shortening  the  muscle  fibers  in  the  walls  of  the  air 
bladder,  or  in  the  walls  of  the  abdomen,  the  air  bladder  is 
made  smaller  and  the  fish  sinks.  By  relaxing  the  muscles 
the  air  expands,  the  fish  as  a  whole  is  relatively  lighter, 
and  consequently  rises. 

Most  fishes  have  swim  bladders,  and  stay  in  midwater, 
that  is,  do  not  rest  most  of  the  time  on  the  bottom.  On 
the  other  hand,  many  fishes  that  rest  most  of  the  time  on 
the  bottom  are  without  a  swim  bladder.  In  some  fishes,  as 
the  perch,  the  air  bladder  is  attached  to  the  walls  of  the 
abdomen.  In  others,  for  example,  suckers,  the  air  bladder 
is  free  from  the  walls  of  the  abdomen  and  is  readily 
removed,  and  in  dressing  the  fish  the  air  bladder  is  taken 
out  with  the  other  internal  organs. 

Locomotion  of  Fishes.  —  Most  fishes  have  the  body  com- 
pressed ;  that  is,  flattened  from  side  to  side.  The  thickest 
part  of  the  body  is  in  front  of  the  middle.  The  longer 
taper  is  toward  the  tail,  and  this  gives  greater  flexibility 
and  freedom  of  motion  to  this  part.  When  the  fish  wishes 
to  swim,  it  makes  a  sideways  and  backward  stroke  of  the 
tail.  This  sends  the  body  ahead  and  sideways ;  that  is,  if 
the  tail  is  struck  back  and  to  the  right  it  pushes  the  fish 


156  Descriptive  Zoology. 

forward  and  to  the  left.  But  the  fish  quickly  makes  an- 
other stroke  in  the  opposite  direction,  and  as  a  result  of 
the  two  he  may  go  straight  ahead.  The  fish  may  simply 
make  the  double  stroke,  right  and  left,  and  without  further 
strokes  dart  straight  forward,  but  usually  there  is  a  suc- 
cession of  strokes  by  which  it  is  enabled  to  pursue  a 
straight  course.  It  should  be  noted  that  nearly  all  fishes 
that  can  swim  rapidly  have  a  pointed  snout  to  diminish  the 
resistance.  Resistance  to  the  motion  of  the  fish  is  still 
further  reduced  by  the  mode  of  overlapping  the  scales  and 
the  coating  of  mucus.  The  fins,  too,  point  backward. 

How  the  Perch  Eats.  —  The  perch  feeds  on  minnows, 
worms,  water  insects,  and  larvae  of  various  sorts,  which  it 
catches  and  swallows  alive.  The  extensibility  of  the  mouth 
is  very  great.  The  upper  jaw  can  be  protruded  so  that 
the  opening  of '  the  mouth  is  a  wide  circle,  nearly  as  large 
as  the  greatest  circumference  of  the  fish  at  any  point.  It 
has  been  noticed  that  when  the  fish  keeps  the  mouth  closed 
the  snout  presents  a  sharp  point ;  this  is  in  marked  con- 
trast with  the  large  opening  shown  when  the  fish  is  about 
to  ingulf  its  prey.  It  must  be  kept  in  mind  that  the  fish 
has  no  special  organs  of  prehension,  but  must  do  all  the 
work  of  catching  with  the  mouth  alone.  There  are 
numerous  teeth,  but  they  are  not  large,  serving  merely  to 
hold  the  struggling  captive,  and  used  little,  if  any,  for  either 
tearing  or  masticating  it. 

Digestive  Organs  of  the  Perch.  —  The  mouth  narrows  back 
into  the  wide  gullet,  which  is  kept  closed  except  when 
swallowing.  The  gullet  leads  into  a  fair-sized  stomach, 
which  ends  blindly  behind.  The  intestine  arises  from  one 
side  of  the  anterior  end  of  the  stomach.  At  the  begin- 
ning of  the  intestine  are  three  short  blind  tubes,  the  ceca. 
The  intestine  takes  one  or  two  turns  and  terminates  in 


Pisces. 


157 


the  anal  opening.  As 
the  perch  is  carnivorous, 
we  should  naturally  ex- 
pect a  relatively  short  in- 
testine. In  the  anterior 
part  of  the  body  cavity 
lies  the  liver.  On  its 
posterior  surface  is  the 
bile  sac,  which  may  be 
greenish  or  yellowish, 
or,  if  empty,  have  little 
color.  It  is  then  hard  to 
discover,  and  appears 
like  a  small  worm-shaped 
appendage  to  the  liver. 
A  duct  conveys  the  bile 
into  the  intestine. 

Circulatory  System  of 
the  Perch. —  The  heart 
of  "the  perch  is  almost 
literally  "in  his  throat." 
The  heart  is  in  a  sepa- 
rate cavity,  the  pericar- 
dial  chamber,  with  a 
firm  partition  between  it 
and  the  main  body  cav- 
ity. The  heart  consists 
of  three  parts,  through 
which  the  blood  passes 
in  order  from  behind. 
The  venous  sinus  re- 
ceives the  blood  from  all 
parts  of  the  body  ;  from 


158  Descriptive  Zoology. 

the  sinus  the  blood  enters  the  auricle,  which  also  is  thin- 
walled  ;  from  the  auricle  it  passes  into  the  ventricle,  whose 
walls  are  thick  and  muscular,  and  by  whose  contraction  the 
blood  is  pumped  clear  around  the  whole  circuit  to  the  heart 
again.  From  the  'anterior  end  of  the  ventricle  runs  for- 
ward the  artery  leading  to  the  gills.  The  first  part  of  the 
artery  is  often  enlarged  and  is  sometimes  called  the  arterial 
cone  or  arterial  bulb.  This  artery  divides  into  four  branches 
on  each  side,  one  to  each  gill.  After  traversing  the  gills, 
the  blood-tubes  (still  called  arteries)  unite  on  each  side,  and 
later  the  two  arteries  thus  formed  unite  to  form  one  dorsal 
artery  which  supplies  all  parts  of  the  body.  The  small 
arteries  subdivide  and  form  capillaries,  which  pervade  all 
the  tissues.  The  capillaries  unite  to  form  the  veins,  which 
again  bring  blood  to  the  heart. 

How  the  Perch  Breathes.  —  When  watching  a  live  fish 
one  sees  that  the  mouth  and  gill  openings  open  and  close 
alternately.  It  can  easily  be  proved  that  water  enters  the 
mouth  and  passes  out  through  the  gill  openings ;  thus  a 
pretty  constant  current  of  water  flows  over  the  gills.  Each 
gill  consists  of  a  bony  arch,  hinged  at  the  upper  and  lower 
ends  and  jointed  in  the  middle.  Along  the  posterior  border 
of  each  gill  is  a  red  fringe,  the  red  color  being  due  to  the 
red  blood  within,  which  shows  through  the  thin,  delicate 
coverings  of  the  gill  filaments,  as  the  individual  parts  of 
the  fringe  are  called.  As  the  blood  comes  up  into  the 
gill  from  the  artery  below,  it  goes  off  into  small  side 
branches  running  out  into  the  filaments ;  when  it  returns 
along  the  other  margin  of  the  gill  filament,  it  enters 
another  artery  to  pass  out  at  the  upper  end  of  the  gill. 
Thus  it  is  clear  that  there  is  a  constant  flow  of  blood  in 
very  narrow,  thin-walled  tubes  in  the  thin-covered  gill, 
filaments;  there  is  also  a  stream  of  fresh  water  flowing 


Pisces. 


159 


over  the  outside  of  the 
filament.  The  blood 
entering  the  gills  has 
lost  oxygen  in  passing 
through  the  muscles 
and  other  working  tis- 
sues of  the  body  ;  so,  in 
passing  through  the 
gills, -it  absorbs  oxygen 
from  the  water  through 
the  comparatively  thin 
wall  that  separates  it 
from  the  water.  On  the 
other  hand,  the  blood 
entering  the  gills  is 
loaded  with  carbon  di- 
oxid  and  other  waste 
matter  that  it  has 
picked  up  in  the  mus- 
cles and  other  tissues ; 
this  passes  out  into  the 
water  and  is  carried 
away.  It  should  be 
noted  that  the  current 
of  water  is  in  the  right 
direction  to  keep  the 
delicate  gill  fringe 
evenly  extended,  in- 
stead of  matting  and 
tangling  it  together,  as 
it  would  be  likely  to  do 
if  the  water  current 
were  reversed. 


160  Descriptive  Zoology. 

The  Protection  of  the  Gills.  —  The  gills  are  really  ex- 
ternal organs.  From  the  nature  of  their  work  they  must 
have  very  thin  external  coatings,  and  so  are  correspond- 
ingly delicate.  Hence  the  strong  yet  flexible  gill  cover. 
The  more  technical  name  for  this  is  the  opercle.  It  con- 
sists of  several  parts,  the  opercle  proper,  subopercle, 
preopercle,  and  interopercle  (see  Fig.  100).  Overlapping 
from  front  to  back,  and  being  under  muscular  control  so 
that  they  can  be  held  down  with  considerable  force  when 
necessary,  they  constitute  a  very  good  shield.  In  addition 
to  the  opercle  there  is  a  gill  cover  below,  called  -the  bran- 
chiostegal  membrane.  It  is  a  tough,  yet  thin,  mem- 
brane supported  by  several  small  curved  bones,  the 
branchiostegal  rays.  A  fish  carries  about  its  head  organs 
that  are  of  vital  importance  and  of  most  delicate  texture, 
yet  it  dashes  among  more  or  less  rough  aquatic  plants  and 
after  fishes  that  are  well  armed  with  spines.  It  is  safe  in 
doing  this  because  of  the  double  set  of  gill  covers,  one  soft 
and  one  bony. 

When  the  perch  swallows  a  spiny  fish,  still  struggling, 
will  not  the  soft  gills  be  torn  from  the  inside,  producing 
serious  injury  ?  The  use  of  the  bony,  toothlike  gill  rakers 
projecting  on  the  inner  surface  of  the  gill  arches  is  now 
apparent.  The  gill  rakers  also  serve  as  a  strainer  in 
swallowing  smaller  particles  of  food,  and  some  authorities 
say  that  the  gill  rakers  serve,  to  a  certain  extent,  as  teeth  in 
crushing  the  food. 

When  the  fish  seizes  its  prey,  it  of  course  takes  water 
into  the  mouth  with  it;  but  this  is  allowed  to  pass  out 
through  the  gill  openings,  and  probably  only  a  little  is  swal- 
lowed with  the  food. 

The  Sense  Organs  of  the  Perch.  —  The  perch  has  well- 
developed  eyes,  but  without  movable  lids.  If  any  one 


Pisces.  161 

doubts  their  keenness  of  sight,  let  him  fish  for  trout  or  black 
bass  before  rendering  his  verdict.  The  sense  of  touch 
seems  well  developed.  Numerous  fishes  have  tactile  bar- 
bels about  the  mouth,  as  the  catfish,  sturgeon,  and  codfish. 
The  lateral  line  is  considered  a  sense  organ.  There  is  an 
internal  ear,  but  it  does  not  appear  that  fishes  hear  ordinary 
sounds  made  out  of  water,  like  human  speech,  unless  they 
are  loud ;  on  the  other  hand,  fishes  have  a  keen  perception 
of  any  sound  vibrations  that  are  directly  transmitted  to  the 
water,  such  as  splashing  in  the  water,  noises  made  by  the 
grating  of  oars  in  the  oarlocks  or  by  hard  objects  striking 
the  bottom  or  sides  of  a  boat.  The  semicircular  canals  are 
now  understood  to  be  connected  with  a  sense  of  equilibrium. 
Smell  is  probably,  pretty  well  developed,  in  some  fishes  at 
least.  The  nostrils  have  nothing  to  do  with  respiration  in 
any  fishes  below  the  lungfishes.  The  nostrils  do  not  open 
into  the  mouth,  but  are  simply  openings  into  a  cavity 
around  which  the  nerves  of  smell  are  distributed.  Some 
fishes  have  a  single  nostril  on  each  side.  In  others,  as  in 
the  perch,  there  are  two  openings  on  each  side.  The  two 
nostrils  of  one  side  connect  with  a  common  cavity,  the 
water  entering  through  one  aperture  and  leaving  through 
the  other.  The  sense  of  taste  is  probably  less  distinct. 

Excretory  Organs  of  the  Perch.  —  The  gills  excrete  car- 
bon dioxid.  For  the  removal  of  nitrogenous  waste  matter, 
there  is  a  pair  of  slender  red  kidneys  which  extend  the 
whole  length  of  the  body  cavity.  They  can  be  seen 
through  the  dorsal  wall  of  the  air  bladder.  There  is  an 
enlargement  at  the  anterior  end  in  front  of  the  air  bladder. 
At  the  posterior  end  there  is  a  tube,  the  ureter,  to  convey 
the  excretion  to  the  exterior ;  this  duct  joins  a  small  uri- 
nary bladder  and  opens  just  back  of  the  opening  of  the  ovi- 
duct, so  that  the  three  openings  at  this  place  are,  in  order 


1 62  Descriptive  Zoology. 

from  the  front,  the  anus,  the  opening  of  the  oviduct,  and 
the  opening  of  the  ureter.  In  most  of  the  higher  fishes 
these  three  openings  are  separate. 

Development  of  the  Perch.  —  The  ovary  is  an  elongated 
body,  occupying,  when  the  eggs  are  mature,  a  large  part  of 
the  space  in  the  body  cavity.  The  outlet  of  the  ovary  is 
the  oviduct,  whose  external  opening  is  just  back  of  the 
anus.  The  ovary  shows  that  it  is  really  a  double  organ  by 
its  forked  anterior  end.  In  the  male  the  two  white  sper- 
maries  unite  in  one  sperm  duct,  which  reaches  the  exterior 
just  behind  the  anal  opening.  The  eggs  are  fertilized 
after  they  have  been  laid.  They  are  left  without  care  on 
the  part  of  the  parents.  The  eggs  contain  a  store  of  nour- 
ishment which  is  not  yet  completely  absorbed  when  the 
tiny  fish  begins  to  swim.  The  young  fishes  feed  at  first  on 
small  crustaceans  and  other  minute  forms  of  life.  Both 
the  eggs  and  the  young  fishes  are  eaten  in  great  numbers 
by  many  kinds  of  fishes  and  other  voracious  water  animals. 

Scales.  —  Scales  are  developments  of  the  deeper  skin  or 
dermis,  serving  for  protection,  or  ornament,  or  both.  The 
scales  usually  overlap  each  other  so  much  that  only  a  small 
part  of  each  scale  is  exposed,  and  this  part  is  covered  by 
the  epidermis.  The  scales  are  usually  of  horny  material 
and  not  bony,  except  in  a  few  fishes,  such  as  ganoids. 

Kinds  of  Fish  Tails.  —  When  the  tail  is  completely  sym- 
metrical, inside  and  outside,  it  is  called  diphycercal.  In 
most  fishes  the  tail,  while  externally  symmetrical,  is  not  so 
within,  the  spinal  column  being  turned  up  as  it  joins  the 
tail  fin  ;  such  a  tail  is  homocercal.  When  the  tail  is  unsym- 
metrical,  with  the  spinal  column  extending  into  the  upper 
lobe,  the  tail  is  said  to  be  heterocercal.  It  is  noteworthy 
that  the  tails  of  nearly  all  young  fishes  are  heterocercal. 


Pisces.  1 63 

The  Fins.  —  The  ordinary  fin  has  a  set  of  fanlike  rays 
supported  by  a  series  of  bones  at  the  base  of  the  fin. 
Fins  are  designated  as  "  soft-rayed "  or  "  spiny-rayed," 
according  to  the  nature  of  the  supporting  rays. 

The  dorsal,  anal,  and  caudal  fins  are  called  median,  as 
they  are  in  the  middle  plane  of  the  body.  The  pectoral 
and  pelvic  are  spoken  of  as  "  paired  fins,"  and  are  com- 
parable to  the  two  pairs  of  limbs  of  the  higher  vertebrates. 

Uses  of  the  Different  Fins.  —  As  already  noted,  the  tail 
fin  is  the  chief  propelling  power.  It  also  serves  as  a  rud- 
der in  guiding  the  direction  of  movement.  The  paired  fins 
serve  as  balancing  organs  and  also  serve  in  elevating  or 
depressing  the  body.  The  dorsal  and  anal  fins  act  like 
the  keel  of  a  boat  in  steadying  and  guiding  the  movement. 

The  Air  Bladder.  —  The  air  bladder  is  generally  consid- 
ered as  comparable  with  the  lung  of  the  higher  forms.  It 
certainly  acts  as  an  organ  of  respiration  in  the  lungfishes 
and  some  of  the  ganoids. 

But  in  most  fishes  the  air  bladder  acts  as  an  organ  for 
maintaining  the  fish's  position  in  the  water,  and  hence  is 
more  appropriately  spoken  of  as  a  "  swim  bladder."  In 
the  lungfishes  and  some  ganoids  the  air  bladder  has  a  wide 
and  direct  connection  with  the  gullet ;  in  many  other  fishes 
the  opening  persists,  but  is  less  direct.  On  the  other 
hand,  in  many  fishes  the  duct  is  entirely  closed.  The  air 
bladder  may  have  thin  walls  or  thick ;  it  may  be  in  one 
section  or  divided  into  several  sections  ;  it  may  be  attached 
to  the  body  wall  or  lie  freely  in  the  body  cavity. 

Flatfishes.  —  Fishes  may  be  flattened  in  two  ways : 
(i)  from  side  to  side,  that  is,  laterally,  when  they  are  said 
to  be  "  compressed,"  as  in  the  ordinary  fish,  more  mark- 
edly shown  in  the  fresh-water  sunfishes;  (2)  a  fish  that 
is  flattened  from  above,  or  dorso-ventrally,  is  said  to  be 


164  Descriptive  Zoology.   . 

"depressed,"  as  with  the  rays.  The  flounders  are  com- 
pressed, but  have  turned  down  on  one  side. 

Electric  Fishes.  —  These  fishes  have  the  power  of  giving 
an  electric  shock  when  touched.  The  electrical  apparatus 
is  a  modification  of  the  muscular  system,  and,  like  the 
muscles,  is  under  the  control  of  the  nervous  system.  It  is 
a  point  to  be  noted  that  the  electric  fishes  are  devoid  of 
scales.  The  torpedo  of  the  Atlantic  coast  and  of  the 
Mediterranean  belongs  to  the  rays.  An  African  catfish 
has  the  same  power,  and  in  South  America  is  found  the 
electric  eel.  It  is  said  that  in  South  Africa  the  natives 
drive  herds  of  horses  into  the  pools,  and  after  the  electric 
eels  have  exhausted  their  "  shocking  power  "  on  the  horses, 
the  eels  may  be  caught  and  handled  with  impunity. 

Colors  of  Fishes.  —  The  colors  of  fishes  are  due  to  two 
factors,  the  nature  of  the  scales  and  the  pigment  in  the 
epidermis.  The  scales  often  are  striated  or  polished  to 
give  various  colors,  especially  the  gleam  so  often  seen  on 
the  sides  of  a  fish.  Aside  from  this  kind  of  appearance  the 
color  is  chiefly  due  to  pigment.  As  in  most  animals,  the 
color  's  darker  on  the  back  than  below,  where  we  often  find 
white.  The  olive  or  dark  back  of  most  fishes  makes  it 
difficult  to  see  them  when  looking  down  into  the  water, 
while  the  white  color  beneath  might  make  a  fish  less  con- 
spicuous to  an  enemy  below  him.  In  the  breeding  season 
many  fishes,  especially  the  males,  assume  much  brighter 
colors,  most  accented  on  the  fins.  Many  fishes,  notably 
catfishes,  change  their  color  considerably  in  conformity 
with  their  surroundings,  like  the  amphibians  and  lizards. 

Care  of  the  Eggs  and  Young.  —  Most  fishes  give  no  care 
whatever  to  the  eggs  or  young.  Some  deposit  the  eggs  in 
a  place  of  comparative  safety.  The  stickleback  builds  a 
nest  for  the  eggs  and  the  male  defends  them  carefully. 


Pisces.  165 

But  the  eggs  of  many  fishes  are  eaten  by  thousands  by  many 
kinds  of  fishes  and  other  animals.  The  very  great  num- 
ber of  eggs  laid  by  most  fishes  is  in  keeping  with  the  fact 
that  the  chances  are  many  to  one  against  their  success- 
ful development.  Indeed,  if  the  eggs  all  developed, 
it  is  easy  to  see  that  the  ocean  would  be  overrun.  For 
instance,  the  codfish  is  said  to  lay  about  eight  million 
eggs  yearly ;  .if  each  of  these  eggs  developed,  it  would  not 
take  long  literally  to  fill  the  ocean.  Contrast  this  "  infant 
mortality"  with  that  of  the  fulmar  petrel.  This  is  said 
to  be  the  most  numerous  bird  in  the  world,  though  it  lays 
but  a  single  egg ;  but  the  conditions  are  such  that  the 
chances  of  this  single  egg  for  reaching  maturity  are  ex- 
tremely favorable. 

Migration  of  Fishes.  —  The  salmon,  shad,  and  sturgeon 
pass  from  the  sea  up  rivers  to  spawn.  The  eels  pass  from 
rivers  into  the  sea  to  lay  their  eggs.  Aside  from  migrat- 
ing to  find  suitable  breeding  grounds,  fishes  migrate  more 
or  less  in  search  of  food.  With  some  kinds  their  move- 
ments are  pretty  regular  and  well  known ;  in  other  cases 
their  location  at  any  given  season  is  very  uncertain,  depend- 
ing on  their  food  and  other  conditions  not  accounted  for. 

Deep-sea  Fishes.  —  Most  fishes  are  found  near  shore  or 
in  comparatively  shallow  water.  Of  those  found  in  deeper 
waters,  it  is  interesting  to  observe  that,  as  the  water  be- 
comes deeper,  and  the  amount  of  light  consequently  less, 
the  fishes  usually  have  larger  eyes,  or  else  a  better  develop- 
ment of  the  organs  of  touch.  In  the  deepest  water  many 
are  phosphorescent,  and  blind  fishes,  or  fishes  with  rudi- 
mentary eyes,  are  found. 

The  Food  Fishes.  —  Among  the  principal  food  fishes  are 
the  codfish,  salmon,  haddock,  shad,  mackerel,  hake,  smelt, 
sardine,  menhaden,  mullet,  lake  trout,  whitefish,  sturgeon, 


1 66*  Descriptive  Zoology. 

halibut,  flounder,  herring,  catfish,  various  kinds  of  bass,  both 
fresh-water  and  marine,  pike,  pickerel,  sucker,  buffalo,  carp, 
and  many  others.  Space  will  not  permit  an  account  of 
them  here,  but  the  student  is  referred  to  the  Riverside 
Natural  History,  and  other  works  of  the  same  scope. 

Artificial  Propagation  and  Distribution  of  Fishes.  —  In 
late  years  much  has  been  done  toward  protecting  and 
propagating  our  edible  fishes.  With  the  increase  of  popu- 
lation the  food  question  will  gradually  become  a  more  and 
more  serious  one.  An  excellent  authority  has  said  that  an 
acre  of  water  ought  to  supply  as  much  food  as  an  acre  of 
land.  The  time  has  passed  when  the  privilege  is  extended  to 
any  one  to  fish  anywhere  and  at  any  time.  Common  sense 
dictates  fhat  fishes  should  not  be  caught  during  their  breed- 
ing season,  and  that  they  should  not  be  caught  under  a  cer- 
tain size,  etc. ;  hence  laws  limiting  the  fishing  season,  and 
requiring  that  seines  must  have  meshes  not  less  than  a  given 
size.  Killing  fishes  by  the  use  of  dynamite  is  prohibited. 
Also  it  is  provided  that  there  shall  be  no  obstruction  to  the 
free  passage  of  fishes  up  and  down  streams ;  and  that 
where  dams  are  necessary,  side  channels  (fish  ways)  shall 
be  provided. 

Most  of  the  states  have  enacted  laws  for  the  protection 
of  its  native  fishes.  A  number  of  states  have  made  appro- 
priations for  the  establishment  and  maintenance  of  fish 
hatcheries,  where  fish  are  artificially  hatched.  These  are 
shipped,  to  be  introduced  into  various  waters  where  it  is 
thought  they  will  thrive,  sometimes  to  replenish  a  stock 
that  is  diminished  by  overfishing  or  other  causes ;  in  other 
cases  to  introduce  them  where  they  do  not  naturally  occur. 
The  United  States  government  has  also  taken  the  matter 
in  hand,  and  many  valuable  results  have  been  obtained. 
This  industry  is  comparatively  in  its  infancy,  but  it  promises 


Pisces. 


to  increase  greatly  the  world's  food  supply.  It  remains  to  be 
seen  what  can  be  done  toward  getting  rid  of  the  more 
voracious  fishes  that  destroy  so  many  of  the  young  of  the 
food  fishes.  The  pikes,  including  the  pickerel  and  mas- 
calonge  of  the  tributaries  of  the  Mississippi  and  St.  Law- 
rence, must  greatly  reduce  the  numbers  of  more  valuable 
fishes.  If  they  were  to  increase  rapidly,  they  might  nearly 
deplete  the  waters,  so  active  ajid  voracious  are  they. 


CHAPTER   XI. 
BRANCH   CHORDATA. 

CLASS    PISCES    (Continued). 
The  Elasmobranchs. 

THE  sharks  and  rays  are  the  chief  representatives  of  the 
subclass  designated  Elasmobranchii.  They  are  nearly  all 
marine.  One  of  the  best  representatives  is  the  shark 
known  as  the  "dogfish,"  which  is  caught  in  large  numbers 
along  the  New  England  coast  for  the  sake  of  the  oil  ob- 
tained from  the  livers.  It  differs  from  the  "  true  fishes  " 
in  the  following  points  :  — 

1.  The  skeleton  is  cartilaginous,  never  bony. 

2.  There  is  no  gill   cover,  the  gill  slits  (usually  five) 
opening  separately. 

3.  The  mouth  and  nostrils" open  ventrally. 

4.  The  scales  are  small  and  separate,  making  the  skin 
rough. 

5.  The  tail  is  heterocercal,  —  that  is,  the  spinal  column 
extends  up  into  the  upper  lobe. 

6.  The  eggs  are  few  and  large,  inclosed  in  a  tough  case, 
the  walls  being  strengthened  by  chitin.     In  some  sharks, 
as  the  dogfish,  the  young  are  brought  forth  alive. 

7.  There  is  no  air  bladder. 

The  Sharks.  —  The  typical  shark  has  a  spindle-shaped 
body,  and  is  exceedingly  active.  The  mouth  is  far  back 
under  the  head  instead  of  in  front,  as  in  most  bony  fishes. 

1 68 


Pisces. 


169 


The  gill  openings  are  separate.  The  teeth  are  flat,  three- 
cornered,  and  sharp.  There  is  a  constant  succession  of 
teeth,  so  that  as  those  of  the  front  row  are  lost,  others  take 
their  place  from  behind.  Though  sharks  are  very  vora- 
cious, it  does  not  follow  that  they  always  attack  human 


FIG.  103.    SHARK  (DOGFISH). 

Showing  separate  gill  slits.     Tail  heterocercal. 

beings.  For  instance,  on  the  coast  of  North  Carolina  sharks 
are  abundant  and  of  large  size  ;  yet  they  do  not  attack  man. 
This  is  probably  because  fishes  are  abundant  and  the 
sharks  have  an  ample  supply  of  food.  But  in  some  parts 
of  the  world  sharks  are  exceedingly  dangerous. 

The  Rays.  —  The  skates  and  rays  have  a  broad  body, 
partly  due  to  the  merging  of  the  body  into  the  large, 
horizontally  flattened  pectoral  fins.  The  bo'dy  is  usually 


A 


FIG.  104.    SHARK  (DOGFISH),  VENTRAL  VIEW. 

Showing  nostrils,  mouth,  gill  slits,  and  anus. 

rhomboidal,  often  wider  than  long.  One  form  is  called 
the  "barn-door  skate."  They  live  on  the  bottom,  feeding 
on  mollusks,  and  have  pavement  teeth.  Some  have  sharp 


170 


Descriptive  Zoology. 


spines  above  the  base  of  the  tail,  and  are  called  "  thorn- 
backs  "  and  "  sting  rays."  Perhaps  the  largest  of  them  is 
the  "devilfish,"  sometimes  attaining  a  width  of  eighteen 
feet  and  a  weight  of  several  tons. 

Some  of  the  rays  have  a  complicated  electric  apparatus, 


FIG.  105.    COMMON  SKATE  (RAY). 

Jaws  and  teeth  (above);  mouth  and  gill  slits  (below). 
From  Packard's  Zoology. 

with  which  they  can  give  a  strong  shock  to  an  animal  with 
which  they  come  in  contact.  This  serves  both  as  a  means 
of  defense  and  for  securing  prey.  The  one  electric  ray 
found  on  the  Atlantic  coast  has  the  scientific  name  Torpedo 
and  the  common  names  "  crampfish  "  and  "numbfish." 


THE   BONY   FISHES. 


The  great  majority  of  fishes  differ  from  the  sharks  and 
rays  as  follows  :  — 

I.    The  skeleton  is  bony  instead  of  cartilaginous. 


Pisces. 


171 


2.  The  gills  are  protected  by  a  gill  cover,  so  that  there 
is  but  one  external  opening. 

3.  The  eggs  are  small  and  numerous. 

The  Spiny-rayed  Fishes.  —  The  perch  is  typical  of  a 
large  group  of  fishes,  all  of  which  have  spiny  rays.  The 
perch  is  widely  distributed  in  fresh-water  lakes  and  streams ; 
the  sea  perch,  or  cunner,  is  common  along  the  Atlantic 
coast,  and  is  so  nearly  like  the  yellow  or  "ringed"  perch 
that  the  descriptions  and  directions  for  dissection  will  apply 
fairly  well  to  it. 

In  the  same  family  with  the  perch  is  the  pike  perch, 
better  known  as  the  "  wall-eye "  or  wall-eyed  pike,  an 
excellent  food  fish.  Among  the  perches  are  also  the 
darters,  a  most  interesting  family  on  account  of  their  small 
size  and  peculiar*  habits.  They  rest  on  the  bottom,  never 
poising  in  the  water  like  ordinary  fishes ;  they  are  found 
in  streams,  in  rapid  currents,  getting  their  food  under 


FIG.  106.    MACKEREL. 

stones,  etc.  They  swim  by  means  of  their  pectoral  fins, 
coming  to  rest  after  the  quick,  darting  motion  that  gives 
them  their  name.  One  species  is  only  from  an  inch  to  an 
inch  and  a  half  long.  Yet  in  some  respects  they  are  to  be 
classed  among  the  most  highly  developed  of  fishes.  They 
may  be  caught  in  a  minnow  seine  by  taking  pains  to  "keep 
the  lead  line  downs"  that  is,  by  being  careful  to  drag  very 


172 


Descriptive  Zoology. 


close  to  the  bottom.  In  keeping  with  the  fact  that  they 
stay  on  the  bottom  is  the  fact  that  most  of  them  lack  an 
air  bladder.  They  feed  mostly  on  insect  larvae. 

The  sunfishes  are  a  closely  related  family ;  these  are 
well  known  as  having  short,  deep  bodies,  usually  with 
bright  colors.  More  active  than  the  sunfishes  proper, 
though  in  the  same  family,  is  the  black  bass,  so  well  known 
as  a  game  fish.  There  are  also  the  white  bass,  striped 
bass,  and  yellow  bass  in  fresh  waters,  and  various  kinds  of 
sea  bass.  Two  important  families  of  the  spiny-rayed  fishes 
are  the  mackerels  and  the  codfishes. 


FIG.  107.    CODFISH. 

Most  of  these  fishes  are  very  active  and  reckoned  among 
the  "  game  fishes  "  on  account  of  their  resistance  to  being 
caught  and  the  skill  required  to  capture  them. 

The  Black  Bass.  —  The  black  bass  is  probably  more 
sought  by  the  scientific  angler  than  any  other  fish  in  the 
Central  States.  It  is  a  fine  type  of  the  spiny-rayed  fishes. 

"  The  black  bass  is  eminently  an  American  fish ;  he  has 
the  faculty  of  asserting  himself  and  making  himself  com- 
pletely at  home  wherever  placed.  He  is  plucky,  game, 
brave,  unyielding  to  the  last  when  hooked.  He  has  the 


Pisces. 


'73 


arrowy  rush  and  vigor  of  a  trout,  the  untiring  strength  and 
bold  leap  of  a  salmon,  while  he  has  a  system  of  fighting 
tactics  peculiarly  his  own.  I  consider  him,  inch  for  inch 
and  pound  for  pound,  the  gamest  fish  that  swims."  —  J.  A. 
HENSHALL. 

The  Catfishes.  —  The  catfishes  are  scaleless ;  they  have 
long,  tapering  barbels  ("feelers")  around  the  mouth;  the 
mouth  is  wide,  and  the  head  low  and  flat,  adapting  the  fish 
for  a  groveling  life,  skimming  along  the  bottom.  The 
dorsal  and  the  pectoral  fins  each  have  for  the  first  ray  a 
very  strong,  stiff  spine,  with  a  jagged  edge,  by  means  of 


FIG.  108.    CATFISH;  CHANNEL  CAT. 

which  they  inflict  painful  and  probably  poisonous  wounds. 
They  seem  to  be  lovers  of  muddy  streams,  and  lead  a 
rather  sluggish  life.  They  abound  in  the  Mississippi  Val- 
ley, where  some  species  reach  a  weight  of  150  pounds. 
They  are  esteemed  as  food,  as  the  flesh  is  of  fair  quality 
and  unusually  free  from  bones. 

The  Suckers.  —  In  this  family  are  a  number  of  forms, 
such  as  the  various  suckers,  the  buffalo  fishes,  and  carps, 
including  some  carps  that  have  been  introduced  from 
Europe.  The  scales  are  large,  with  smooth  borders ;  such 
scales  are  called  cycloid  scales.  They  all  have  a  scaleless 


174  Descriptive  Zoology. 

head  and  a  sucking  mouth,  toothless,  with  soft  lips  capable 
of  downward  extension ;  they  feed  to  a  large  extent  on 
vegetable  matter,  hence  have  a  long  intestine,  in  marked 
contrast  with  the  short  intestine  of  the  carnivorous  perch. 
The  air  bladder  is  large,  and  is  constricted  into  two  or 
three  compartments,  linked  together  sausagelike.  The 
air  bladder  communicates  with  the  digestive  tube.  They 
ascend  streams  in  the  spring  to  lay  their  eggs.  Their  flesh 
is  rather  tasteless  and  full  of  bones ;  still,  they  are  largely 
used  as  food,  as  they  cost  less  than  other  fishes,  being 
caught  in  immense  numbers  in  seines.  Their  sluggishness 
contrasts  sharply  with  the  alertness  of  the  game  fishes. 


FIG.  109.    ATLANTIC  SALMON. 

From  Kingsley's  Zoology. 

The  Salmon  Family. — The  salmon  is  well  known  both 
from  its  commercial  importance  and  from  its  remarkable 
migrations  up  rivers  to  spawn.  It  passes  swift  rapids  and 
leaps  falls  of  considerable  height.  To  this  family  also 
belong  the  trout  and  the  whitefish  of  the  great  lakes. 

The  Trout.  —  One  of  the  daintiest  of  fishes,  as  well  as 
one  of  the  most  delicately  flavored,  is  the  trout.  On 
account  of  its  wariness  it  is  sought  by  the  angler  who 
wishes  to  overmatch  its  cunning. 

"  This  is  the  last  generation  of  trout  fishers.  The  chil- 
dren will  not  be  able  to  find  any.  Already  there  are  well- 


Pisces. 


175 


trodden  paths  by  every  stream  in  Maine,  in  New  York,  and 
in  Michigan.  I  know  of  but  one  river  in  North  America 
by  the  side  of  which  you  will  find  no  paper  collar  or  other 
evidence  of  civilization.  It  is  the  Nameless  River.  Not 
that  trout  will  cease  to  be.  They  will  be  hatched  by 
machinery  and  raised  in  ponds,  and  fattened  on  chopped 
liver,  and  grow  flabby  and  lose  their  spots.  The  trout  of 


FIG.  no.    THE  RAINBOW  TROUT. 

From  Kellogg's  Zoology. 

the  restaurant  will  not  cease  to  be.  He  is  no  more  like 
the  trout  of  the  wild  river  than  the  fat  and  songless  rice 
bird  is  like  the  bobolink.  Gross  feeding  and  easy  pond 
life  enervate  and  deprave  him.  The  trout  that  the  chil- 
dren will  know  only  by  legend  is  the  gold-sprinkled  living 
arrow  of  the  white  water,  able  to  zigzag  up  the  cataract, 
able  to  loiter  in  the  rapids,  whose  dainty  meat  is  the  glanc- 
ing butterfly."  —  MVRON  W.  REED. 

The  Flatfishes. — As  an  example  of  this  group  we  may 
select  the  flounder  found  along  the  Altantic  coast.  These 
fishes  keep  near  the  bottom,  swimming  on  one  side,  and 
the  two  eyes  are  both  on  the  side  that  is  uppermost.  Per- 
haps the  most  interesting  fact  concerning  these  odd  fishes 
is  their  development.  At  first  they  are  symmetrical,  with 


ij6  Descriptive  Zoology. 

an  eye  on  each  side,  and  erect  like  other  fishes ;  gradually 
the  body  turns  over  to  one  side,  the  cranium  becomes 
twisted,  and  the  eye  of  the  side  that  turns  down  travels 
over  to  the  upper  side ;  the  upper  side  becomes  dark,  while 
the  under  side  is  white  or  nearly  so,  whereas  in  the  young 
flounder  both  sides  were  colored  alike.  The  sole  and  the 
plaice  belong  to  this  family.  The  most  important  member, 


FIG.  in.    WINTER  FLOUNDER. 

From  Kingsley's  Zoology. 

however,  is  the  halibut,  which  sometimes  reaches  a  weight 
of  three  or  four  hundred  pounds. 

Eels.  —  The  eels  have  elongated,  cylindrical  bodies,  with 
minute  scales  or  none.  They  have  no  ventral  fins,  and 
swim  or  crawl  through  the  mud  by  a  snakelike  motion. 
They  are  active  and  very  voracious,  pushing  their  way  under 
stones  and  into  holes  after  small  fishes  and  crustaceans,  on 
which  they  feed.  It  is  said  that  they  can  crawl  a  consider- 
able distance  on  land,  through  wet  grass,  and  that  they 
pass  around  falls  and  other  obstructions  in  this  way. 

Flying  Fish.  —  Certain  marine  fishes  are  called  "  flying 
fishes."  They  do  not  really  fly,  but,  by  means  of  their  long 
pectoral  fins,  make  long  flying  leaps  through  the  air.  They 


Pisces. 


'77 


make  these  leaps  better  against  the  wind  than  in  the  same 
direction  as  the  wind.  Their  leaps  are  probably  somewhat 
like  the  "  sailing"  of  birds. 

THE   GANOIDS. 

We  have  in  the  United  States  four  kinds  of  ganoids,  the 
gar  pike,  the  sturgeon,  the  mudfish,  and  the  spoonbill  catfish. 


FIG.  112.    GAR  PIKE;  GAR. 

The  gar  pike  has  a  cylindrical  body  covered  by  rhom- 
boidal  bony  scales.  These  scales  are  coated  with  enamel, 
making  a  very  strong  and  complete  armor.  The  jaws  ex- 
tend, forming  a  long  bony  snout,  the  nostrils  being  at  the 
tip  of  the  upper  jaw.  The  teeth  are  sharp,  and  the  fish 
is  voracious,  but  of  rather  sluggish  habits.  The  tail  is 
slightly  heterocercal.  Three  species  are  common  in  the 
Mississippi  and  some  of  its  tributaries  :  the  long-nosed  gar 
(Fig.  112);  the  short-nosed  gar;  and  the  alligator  gar, 
which  is  said  sometimes  to  attain  a  length  of  ten  feet. 


FIG.  113.    COMMON  STURGEON. 

After  Goode.  —  From  Kingsley's  Zoology. 


The  sturgeon  is  decidedly  like  a  shark  in  general  ap- 
pearance, with  its  strongly  heterocercal  tail,  its  projecting 
snout,  with  the  mouth  well  back  on  the  ventral  surface,  and 


178  Descriptive  Zoology. 

its  cartilaginous  skeleton.  The  skin  is  also  rough  like  that 
of  a  shark ;  but  in  addition  to  the  separate  scales  that  give 
roughness,  there  are  several  rows  of  bony  plates,  each  with 
a  central  projecting  point.  These  rows  of  scales  are  not 
set  close  together,  one  row  of  large  scales  being  along  the 
back,  with  rows  of  smaller  scales  along  the  sides.  The 
sturgeon  has  a  projectile  toothless  mouth,  and  feeds  along 
the  bottom,  sucking  up  worms,  larvae,  etc.,  from  the  mud. 

The  spoonbill  catfish  very  much  resembles  a  catfish,  being 
smooth-skinned,  but  has  a  long,  paddle-shaped  upper  jaw 
with  which  to  stir  up  the  mud  from  which  it  gets  its  food. 

The  mudfish,  or  bowfin,  is,  in  the  Mississippi  Valley, 
commonly  called  the  "  dogfish,"  an  unfortunate  term  that 


FIG.  114.    MUDFISH;  BOWFIN;  GRINDLE. 

Dogfish  (of  Central  States,  but  should  not  be  confused  with  the  shark  called  dogfish). 

is  likely  to  confuse  it  with  the  shark  called  by  the  same 
name.  The  mudfish,  as  the  name  implies,  lives  in  shallow 
water,  and  is  a  very  voracious  fish.  It  is  more  nearly  like 
the  ordinary  bony  fishes  than  the  other  ganoids,  having  a 
pretty  complete  bony  skeleton.  Its  flesh  is  soft,  and  gen- 
erally considered  as  wholly  unfit  for  food,  but  of  late  it  is 
beginning  to  be  used.  In  some  waters  of  the  Mississippi 
system  it  is  very  abundant. 

These  four  fishes  do  not  present  many  characteristics  in 
common,  hence  it  is  not  strange  that  the  authorities  differ 
greatly  as  to  their  classification.  In  the  first  place,  it  should 


Pisces.  179 

be  noted  that  there  are  but  few  living  ganoids ;  these  are 
the  survivors  of  a  host  that  existed  in  earlier  geologic 
periods.  Many  of  these  fossil  forms  possess  a  heavy 
armor,  of  which  the  gar  shows  a  sample.  It  is  also 
noteworthy  that  North  America  has  a  majority  of  the 
survivors.  Most  of  them  have  heterocercal  tails. 

The  most  valuable  feature  for  our  consideration  is  the 
air  bladder,  which  is  present  in  all,  and  in  all  is  connected 
with  the  gullet  by  a  persistent  open  duct  This  duct  opens 
on  the  dorsal  side  of  the  gullet  except  in  one  instance. 
Further,  the  air  bladder  in  most  has  an  unusual  supply  of 
blood,  so  that  it  serves  to  a  considerable  extent  as  a  lung. 
Both  the  mudfish  and  the  gar  pike  often  come  to  the  sur- 
face and  emit  bubbles  and  take  in  a  fresh  supply  of  air, 


FIG.  115.      LUNGFISH. 
After  Boas.  —  From  Kingsley's  Zoology. 

very  much  as  do  the  mud  puppy  and  the  tadpole  after  the 
lungs  begin  to  develop.  These  two  fishes  are  very  tena- 
cious of  life  when  removed  from  the  water,  undoubtedly 
because  of  the  ability  of  the  air  bladder  to  act  as  a  lung. 
The  ganoids  thus  foreshadow  the  lungfishes,  as,  in  turn, 
the  lungfishes  anticipate  the  Amphibia. 

THE   LUNGFISHES. 

In  the  Jungfishes  the  development  of  the  air  bladder  as 
a  lung  is  much  more  complete  than  in  any  of  the  ganoids. 
The  nostrils  open  into  the  mouth  cavity,  which  is  not  the 


180  Descriptive  Zoology. 

case  with,  any  other  fishes.  There  is  also  a  pulmonary 
artery  and  a  pulmonary  vein,  making  the  circulation  much 
more  perfect.  In  keeping  with  this,  the  auricle  is  partially 
divided  into  two  compartments.  There  are  only  three  or 
four  species,  one  in  Australia,  one  in  Africa,  and  one  or 
two  in  South  America.  The  Australian  form  has  a  single 
lung;  the  others  have  the  lungs  double.  The  African 
lungfish  secures  protection  during  the  dry  season  by 
burying  itself  in  the  mud,  where  it  remains  in  a  snugly 
inclosed  cavity.  These  "  mud  nests,"  as  they  are  called, 
have  been  dug  up  and  the  fish  taken  alive  and  uninjured  to 
Europe.  Gills  are  present  and  permanently  kept. 

It  is  a  general  belief  among  naturalists  that  the  Amphibia 
originated  from  such  lunged  fishes  as  these  we  have  been 
considering.  Why,  indeed,  should  we  hesitate  to  believe 
that  a  race  of  animals  has  gradually  changed  from  an 
aquatic  to  a  terrestrial  life  in  long  course  of  time,  when  we 
have  all  seen  this  change  take  place  in  the  individual  frog 
in  a  relatively  short  time  ?  Whether  they  were  first  led  to 
do  this  from  the  drying  up  of  the  water  or  from  pollution 
of  the  water,  making  it  unfit  for  respiration,  or  whether 
they  were  forced  to  adopt  a  land  life  from  the  competition 
for  a  living  in  the  water,  or  from  some  other  causes  or 
conditions,  who  shall  say  ? 

SUBCLASSES   OF   PISCES. 

'Subclass  i.    Elasmobranchii,  sharks  and  rays. 

f  Teleostei,    the    bony 

_,.  Subclass  2.    Teleostomi.  \      fishes. 

Pisces.  |  _       . ,  .   t  . ,    „ 

[  Ganoidei,  "ganoids. 

Subclass  3.    Dipnoi,  the  lungfishes. 


CHAPTER  XII.  • 
BRANCH   CHORDATA. 

CLASS   AMPHIBIA. 
Example.  — The  Frog. 

Where  Frogs  Live.  —  Frogs  are  usually  found  in  or  near 
water.  In  the  spring  they  congregate  in  ponds  and  pools 
to  lay  their  eggs.  Later  in  the  season  they  scatter,  and 
may  be  found  at  some  distance  from  the  water,  but  still  in 
moist  places,  such  as  near  springs,  swampy  meadows,  etc. 
Even  when  they  are  spending  most  of  the  time  in  the 
water  they  come  out  on  the  banks  to  catch  insects. 

How  the  Frog  Progresses.  — The  frog  has  three  modes  of 
locomotion — jumping,  swimming,  and  creeping  or  walk- 
ing. The  latter  mode  is  seldom  used  except  to  change  its 
position  or  climb  up  something  on  which  to  rest.  The  long, 
muscular  thighs  enable  the  frog  to  make  powerful  leaps,  by 
which  it  rapidly  escapes  to  the  water  when  it  is  on  shore 
and  alarmed.  In  swimming  it  folds  the  fore  limbs  along- 
side the  body  and  by  the  simultaneous  strokes  of  the  two 
hind  limbs,  with  the  long,  broad,  webbed  feet,  makes  rapid 
progress.  It  is  a  model  swimmer. 

The  Frog's  Food  and  Method  of  Eating.  —  The  frog 
feeds  chiefly  on  insects,  though  it  also  eats  slugs,  worms,  and 
various  kinds  of  larvae.  The  writer  has  found  the  remains 
of  a  mouse  in  the  stomach  of  the  common  frog,  and  in  the 
stomach  of  a  bullfrog  a  small  bird  entire ;  but  these  cases 
are  exceptional.  The  frog  catches  insects — its  main 

181 


182 


Descriptive  Zoology. 


food  —  by  means  of  the  tongue.  The  tongue  is  attached 
in  front  and  free  behind.  Insects  are  caught  by  turning 
the  tongue  forward  quickly,  the  sticky  mucus  with  which 
the  tongue  is  covered  holding  them  securely.  There  are 
fine  teeth  on  the  upper  jaw  and  the  roof  of  the  mouth,  but 
these  serve  merely  to  hold  the  insect  or  slimy  worm,  while 
it  is  being  swallowed,  and  are  not  used  for  masticating  the 
food.  The  wide  mouth  narrows  into  the  gullet,  which  is 
really  wide,  since  the  animals  captured  are  swallowed 


FIG.  116.    PLAN  OF  FROG'S  STRUCTURE,  SIDE  VIEW. 

whole,  but  is  kept  closed  by  being  "  puckered  up,"  as  it 
were.  Back  of  the  gullet  is  the  rather  large  stomach. 
The  stomach  narrows  as  it  extends  backwards,  and  is  con- 
tinued into  the  intestine,  which,  after  one  or  two  turns, 
suddenly  widens  into  the  cloaca.  Alongside  the  stomach 
is  the  lobed  liver ;  between  two  of  the  lobes  is  the  bile 
sac,  whose  duct  empties  into  the  intestine  a  short  distance 
behind  the  stomach.  The  duct  from  the  small  pancreas  joins 
the  bile  duct  a  little  before  the  latter  enters  the  intestine. 


Amphibia. 


'83 


How  the  Frog  Breathes.  — The  adult  frog  breathes  chiefly 
by  means  of  lungs.  In  dissecting,  the  lungs  may  be  found 
collapsed;  in  which  case  they  are  small  and  dark-colored. 
When  inflated  they  are  of  considerable  size  and  of  a  beau- 
tiful pinkish  color,  owing  to  the  blood  in  the  capillaries. 
A  frog's  limg  is  not  a  mere  air  sac,  with  transparent  walls, 
as  with  most  fishes.  There  is  blood  circulating  in  the 
wall,  and  the  wall  is  somewhat  thickened,  and  has  ridges 
extending  on  the  inside,  which,  to  a  limited  extent,  parti- 


FIG.  117.    PLAN  OF  FROG'S  STRUCTURE,  VENTRAL  VIEW. 

tion  off  the  space  into  air  vesicles,  thus  increasing  the  area 
of  the  inside  of  the  lungs,  and  consequently  exposing  more 
blood  to  the  action  of  the  air  contained  within  the  lung. 

In  watching  the  breathing  movements  of  the  frog,  three 
actions  are  seen :  first,  the  in-and-out  movement  of  the 
floor  of  the  mouth ;  second,  occasional  movements  of  the 
side  of  the  body ;  third,  opening  and  closing  of  the  nos- 
trils. When  the  floor  of  the  mouth  is  lowered  and  the 
nostrils  are  opened,  air  is  taken  into  the  mouth  cavity ;  if, 
now,  the  nostrils  are  closed  and  the  floor  of  the  mouth 


184  Descriptive  Zoology. 

raised,  air  is  forced  into  the  lungs.  The  gullet  is  kept 
firmly  closed  so  that  air  does  not  enter  it,  and  the  glottis,  a 
longitudinal  slit  in  the  floor  of  the  mouth  just  back  of  the 
tongue,  being  opened  at  the  right  time,  air  freely  enters 
the  lungs.  The  windpipe,  or  trachea,  is  extremely  short, 
dividing  almost  immediately  to  enter  the  two  lungs.  The 
less  frequent  movements  of  the  sides  of  the  body  seem  to 
be  for  driving  air  out.  This  is  accomplished  by  the  action 
of  the  muscles  of  the  sides  of  the  abdomen.  From  the 
above  it  may  be  understood  why  a  frog  may  be  suffocated 
by  having  its  mouth  held  open  for  any  considerable  time. 

The  frog  also  breathes  to  a  limited  extent  by  means  of 
the  skin.  It  has  been  noticed  that  the  skin  is  always 
moist,  a  condition  necessary  for  this  function.  In  cool 
weather  it  will  be  noticed  that  frogs  kept  in  aquariums 
frequently  sink  to  the  bottom  and  remain  there  for  a  long 
time.  Of  course  the  breathing  movements  then  cease. 
The  diminished  activity  is  accompanied  by  a  reduced  re- 
spiratory need,  and  the  blood,,  circulating  in  the  skin, 
absorbs  all  the  oxygen  that  is  required. 

Circulation  of  Blood  in  the  Frog.  —  The  heart  consists  of 
one  ventricle  and  two  auricles.  The  right  auricle  receives 
blood  through  the  .caval  veins  from  all  parts  of  the  body 
except  the  lungs;  this  blood  is  dark  because  it  has  been 
deprived  of  its  oxygen  by  the  working  tissues  of  the  body ; 
it  is  loaded  with  impurities  which  the  tissues  have  given  to 
it.  The  left  auricle  receives  blood  from  the  lungs ;  this 
blood  is  bright-colored  from  the  oxygen  just  obtained  in 
the  lungs ;  it  has  also  lost  some  carbon  dioxid. 

The  two  auricles  contract  at  the  same  time  and  .send 
these  two  kinds  of  blood  into  one  ventricle.  How  is  one 
ventricle  to  send  the  purer  blood  to  the  organs  that  need  it, 
and  the  impure  blood  to  the  organs  whose  work  it  is  to 


Amphibia.  185 

remove  impurities  ?  Without  attempting  here  to  explain 
this  in  detail,  it  may  be  stated  that,  owing  to  the  way  in 
which  the  arteries  branch  from  the  ventricle,  and  to  an 
ingenious  valve  arrangement,  ( I )  the  best  blood  is  sent  to 
the  head,  (2)  the  next  best  blood  (somewhat  mixed)  is  sent 
to  the  body,  and  (3)  the  most  impure  to  the  lungs  and  skin. 

The  Lymphatic  System.  —  In  skinning  the  frog  it  is  very  noticeable 
that  the  skin  is  attached  only  occasionally,  leaving  a  free  space  between 
the  skin  and  muscles  over  the  greater  part  ot  the  body.  In  these 
spaces  is  a  more  or  less  watery  liquid,  the  lymph.  Lymph  is  also  found 
in  the  body  cavity  around  the  internal  organs.  The  lymph  system  is 
part  of  the  blood  system.  Lymph  may  be  described  as  part  of  the 
liquid  of  the  blood  that  has  soaked  out  of  the  regular  blood  tubes  and 
gotten  into  the  lymph  spaces.  There  are  two  pairs  of  contractile 
•'  lymph  hearts,11  one,  whose  pulsations  may  have  been  observed,  near 
the  anus.  The  other  pair  is  between  the  transverse  processes  of  the 
third  and  fourth  vertebrae,  and  cannot  readily  be  found. 

Excretion  of  Impurities.  —  The  lungs  and  skin  remove 
carbon  dioxid  from  the  blood  as  it  circulates  through  them. 
The  nitrogenous  waste  matter  is  taken  from  the  blood  as 
it  flows  through  the  kidneys.  From  each  kidney  a  tube 
called  the  ureter  passes  back  to  open  into  the  cloaca  on 
its  dorsal  surface. 

The  Colors  of  the  Frog.  —  The  prevailing  colors  are  green 
and  brown,  though  some  are  marked  by  black  spots,  and 
sometimes  these  black  spots  are  made  more  distinct  by  a 
whitish  border.  The  frog  does  not  frequent  bare  ground, 
but  is  usually  to  be  found  near  plants,  whether  in  water  or 
on  land.  Its  colors  are  generally  similar  to  the  surround- 
ings, so  that  it  is  not  a  very  conspicuous  object,  and  some% 
times  keen  eyesight  is  needed  to  discover  it  even  when  in 
plain  view.  By  distending  its  lungs  the  frog  easily  floats 
in  water.  When  so  floating  only  the  top  of  the  head  is  out 
of  water,  with  its  three  projecting  points,  the  snout  and 


1 86  Descriptive  Zoology. 

the  two  eyes.  In  some  kinds  of  frogs  the  head  is  more 
distinctly  green  than  other  parts,  so  a  little  practice  is 
required  before  the  collector  readily  discovers  it  as  it  rests 
in  the  water,  with  the  top  of  the  head  appearing  among 
green  leaves. 

The  color  is  due  to  pigment  cells  in  the  deep  layer  of  the 
skin.  These  cells  are  branched,  but  can  change  their  shape 
and  vary  the  color  somewhat  in  accordance  with  the  sur- 
roundings. These  cells  may  easily  be  observed  in  the  skin 
of  the  frog's  web,  and  can  hardly  escape  observation  when 
the  circulation  in  the  web  is  studied. 

The  Frog's  Enemies. —  Most  of  the  larger  snakes  eat  frogs 
when  they  can  get  them.  Many  fishes  take  them  greedily, 
hence  the  frog  is  used  as  bait.  A  number  of  birds  capture 
frogs,  including  some  of  the  hawks,  certain  waders,  and 
perhaps  others. 

The  frog's  color  undoubtedly  often  keeps  it  from  being 
discovered,  and  when  it  is  approached  it  can  make  use  of 
one,  or  both,  of  its  two  speedy  modes  of  locomotion  to  make 
good  its  escape ;  concealment  by  protective  resemblance 
and  escape  by  flight  are  its  two  safeguards,  for  it  has  no 
weapons  of  defense. 

How  Frogs  spend  the  Winter.  —  At  the  approach  of  freez- 
ing weather  frogs  reassemble  at  the  shore,  and  perhaps  for 
some  time  may  be  found  at  the  surface  during  the  warmer 
part  of  the  day,  but  stay  at  the  bottom  during  the  night  or 
during  colder  days.  They  finally  dive  deep  into  the  mud, — 
which  is  their  winter  resort.  Here  they  hibernate,  motion- 
less, eyes  closed,  lungs  emptied,  with  no  breathing  move- 
ments, the  heart  beating  feebly  and  slowly,  till  they  are 
revived  by  the  returning  warmth  of  spring. 

Warm-blooded  vs.  Cold-blooded  Animals.  —The  frog's  nor- 
mal temperature  during  the  season  when  it  is  active  is  a 


Amphibia.  187 

little  above  the  surrounding  air  or  water.  Its  temperature 
varies  with  the  degree  of  its  activity.  In  the  winter  when 
it  is  buried  in  the  mud  its  temperature  sinks  nearly  to  the 
freezing  point,  for  the  lower  layers  of  water  have  a  tem- 
perature of  about  40°  F.  In  other  words,  the  frog's  tem- 
perature is  variable,  instead  of  constant  as  in  the  case  of 
mammals. 

The  Nervous  System  of  the  Frog.  —  The  widest  part  of 
the  brain  consists  of  the  two  optic  lobes.  In  front  of  these 
are  the  two  cerebral  hemispheres.  Barely  separated  from 
the  anterior  ends  of  the  cerebral  hemispheres  by  a  slight 
groove  are  the  olfactory  lobes ;  they  seem  to  be  a  part  of 
the  cerebral  hemispheres.  Back  of  the  optic  lobes,  sepa- 
rated by  a  depression,  is  the  cerebellum,  a  narrow  trans- 
verse band.  Beyond  the  cerebellum  is  the  spinal  bulb  (see 
also  Fig.  167).  There  are  ten  pairs  of  cranial  nerves. 
There  are  also  ten  pairs  of  spinal  nerves. 

The  Senses  and  Sense  Organs  of  the  Frog.  —  The  promi- 
nence of  the  frog's  eyes  has  already  been  noticed.  The 
upper  lid  is  thick  and  drops  with  the  eye  when  it  is  with- 
drawn. The  thin  under  lid  can  be  drawn  more  completely 
over  the  eye  and  is  often  used  when  the  upper  lid  remains 
stationary.  Back  of  the  eye  the  eardrum  is  conspicuous. 
From  the  inner  surface  of  the  tympanum  extends  the  bony 
rod  called  the  "  columella  "  to  the  inner  ear,  to  which  it 
transmits  the  vibrations  received  by  the  tympanum.  The 
sense  of  taste  is  apparently  well  developed.  All  parts  of 
the  skin  seem  to  possess  the  sense  of  touch.  The  nostrils 
open  directly  into  the  front  of  the  mouth.  Of  the  sense  of 
smell  less  is  known  than  of  the  other  senses. 

Development  of  the  Frog.  —  The  eggs  are  formed  in  the 
ovaries.  When  the  eggs  are  mature  the  ovaries  become 
much  folded  and  plaited  and  the  egg-masses  occupy  a  large 


i88 


Descriptive  Zoology. 


share  of  the  space  in  the  body  cavity.     The  eggs  finally  are 
set  free  in  the  body  cavity ;  they  find  their  way  to  the  open- 


Nasal  sac 


Eye 


Cerebrum 


Spinal  bulb 

t 

Boundary  between 

I 
Spinal  cord  - 


Spinal  nerves  ,. 


Branches  connecting    ,•' 
t 


Sympathetic  gan-  *' 
glions 


Sympathetic  gan- / 

glion 


Olfactory  nerve 


Optic  nerve 

Ganglion  of  fifth 

nerve 

Fifth  nerve 
Ganglion  of  vagus 

nerve 
Vagus  nerve 


First  spinal  nerve 
Brachial  nerve  (arm) 


Sympathetic  nerve 
trunk 


.     Sympathetic  gan- 
glions 


Sciatic  nerve  (thigh) 


FIG.  118.    NERVOUS  SYSTEM  OF  FROG,  VENTRAL  VIEW. 


Amphibia.  189 

ing  at  the  inner  end  of  the  oviduct  and  as  they  pass  along 
the  duct  are  coated  with  a  layer  of  gelatinous  material 
which  swells  up  after  the  eggs  are  laid,  so  that  each  egg 
appears  as  a  small,  spherical,  glassy  body,  with  its  upper 
part  of  a  dark  color,  and  surrounded  by  a  spherical  mass  of 
clear,  jellylike  substance.  In  a  few  weeks  the  form  of  the 
body  begins  to  appear.  The  tail  begins  to  vibrate,  the  sur- 
rounding mucus  breaks  up  and  the  tadpole  emerges  with  gills 
—  very  much  like  a  tiny  fish.  For  a  short  time  there  is  no 
mouth  opening,  and  the  little  tadpole  attaches  itself  to  water- 
weeds  by  suckers  near  the  place  where  the  mouth  is  to 


FIG.  119.    DEVELOPMENT  OF  A  TOAD. 

From  Packard's  Zoology. 

appear.  After  the  mouth,  with  horny  lips  and  jaws,  is 
developed,  the  tadpole  feeds  greedily  on  waterweeds  and 
grows  rapidly.  The  external  gills  disappear  and  are  replaced 
by  internal  gills,  which  are  concealed  by  a  fold  of  skin  which 
incloses  a  gill  chamber.  There  is  an  opening  on  the  left 
side  of  the  body  for  the  water  to  escape.  The  limbs  de- 
velop as  little  projections,  like  buds,  on  the  sides  of  the 
body  ;  but  the  anterior  limbs  are  for  a  long  time  concealed 
by  the  gill  chamber  and  therefore  appear  to  develop  later 
than  the  hinder  pair.  At  first  the  tadpole  swims,  fishlike, 
wholly  by  means  of  the  tail,  and  it  continues  to  do  so  long 
after  the  limbs  appear.  It  holds  the  limbs  close  by  the  side 


190  Descriptive  Zoology. 

of  the  body  and  swims  by  the  sidewise  movements  of  the 
tail.  At  this  time  the  intestine  is  long  and  coiled  spirally. 
Then  for  a  time  the  tadpole  quits  eating.  It  fasts,  but  is 
maintained  by  the  material  from  its  tail,  which  is  being 
absorbed  while  a  great  transformation  is  taking  place.  The 
horny  lips  and  jaws  are  shed,  the  mouth  becomes  wider  and 
develops  true  jaws  with  teeth.  The  long,  coiled  intestine 
becomes  relatively  short.  The  anterior  limbs  are  pushed 
out  through  the  fold  of  the  skin  that  inclosed  them.  Lungs 
are  developed,  although  they  are  at  first  but  little  used,  the 
tadpole  coming  to  the  surface  occasionally  to  get  a  mouth- 
ful of  air ;  respiration  is  still  chiefly  accomplished  by  the 


Gills 


FIG.  120.    THE  SIREN  ;  MUD  EEL. 

Gills  persistent. 

gills,  but  the  lungs  come  to  be  used  more  and  the  gills  less 
until  finally  the  gills  disappear.  It  was  herbivorous ;  now 
it  is  carnivorous.  Formerly  strictly  aquatic,  it  is  now  am- 
phibian. In  short,  our  tadpole  has  become  a  frog. 

CLASSIFICATION   OF   AMPHIBIA. 

The  Siren.  —  The  lowest  of  the  amphibians  is  the  siren 
or  mud  eel.  It  is  eel-like  in  form,  having  gills  that  persist 
through  life,  and  one  pair  of  legs  (the  anterior).  It  lives 
in  the  swamps  of  the  Southern  states  and  sometimes  is 
three  feet  long. 


Amphibia. 


191 


The  Mud  Puppy.  —  The  mud  puppy,  or  water  dog,  is  a 
little  higher  than  the  siren,  having  two  pairs  of  legs.  It 
also  has  persistent  external  gills.  It  is  found  in  the  streams 


FIG.  121.    NECTURUS;  MUD  PUPPY  (NORTH);  WATER  DOG  (SOUTH). 

Gills  retained  thruout  life. 

of  the  Mississippi  Valley  and  in  the  lakes  of  central  New 
York.     It  sometimes  'attains  a  length  of  two  feet. 


FIG.  122.    SPOTTED  SALAMANDER. 

The  Salamanders.  —  The  salamanders  are  still  a  step 
higher.  They  have  gills  in  the  earlier  stage,  but  shed  them 
when  adult.  They  retain  the  tail,  and,  in  swimming,  fold 


192  Descriptive  Zoology. 

the  two  pairs  of  limbs  close  to  the  body  and  swim  by  lat- 
eral movements  of  the  vertically  flattened  tail.  Most 
of  the  salamanders  li^e  on  land,  but  they  seek  moist 
places.  The  salamanders  are  often  incorrectly  called  liz- 
ards. They  are  pretty  well  distributed  in  temperate  and 
tropical  regions.  Most  of  them  are  of  rather  small  size. 
One  form  is  used  as  food  by  the  Mexicans.  In  some 
forms  the  larva  is  larger  than  the  adult.  In  unfavorable 
conditions  some  of  the  larvae  fail  to  transform,  but  perma- 
nently, or  at  least  indefinitely,  retain  the  gills.  Some 
European  forms  fail  to  develop  lungs.  Many  of  the 
salamanders  reproduce  the  legs  or  tail  when  these 
members  have  been  lost.  Like  the  other  amphibians,  the 
salamanders  go  to  the  water  to  lay  their  eggs,  and  all  sala- 
manders, whether  they  lead  a  terrestrial  life  later  or  not, 
spend  their  early  life  in  the  water,  breathing  by  means  of 
gills.  One  family  of  salamanders  are  called  newts  or  efts. 
None  of  o'ur  amphibians  are  in  any  way  poisonous  or  inju- 
rious to  man,  though  several  of  them  are  reputed  to  be  so. 

Frogs  and  Toads.  —  These  are  the  highest  of  the  amphib- 
ians. They  have  lost,  not  only  the  gills,  but  also  the 
tail.  They  are  not  only  fitted  to  live  a  truly  terrestrial 
life,  like  the  salamanders,  but  are  much  more  active  than 
the  latter,  having  the  hind  limbs  well  developed  for  leap- 
ing, whereas  the  two  pairs  of  limbs  in  the  salamander  are 
nearly  equal,  and  it  can,  at  best,  only  crawl. 

One  of  the  commonest  of  the  frogs  is  the  leopard  frog, 
so  named  from  its  spots.  Quite  similar  to  it  in  general 
appearance  is  the  pickerel  frog.  The  green  frog  is  green- 
ish and  brownish,  with  small  dark  spots.  The  bullfrog  is 
well  known  from  its  size  and  heavy  voice. 

The  common  toad  has  a  rough-looking,  warty  skin,  in 
which  are  glands  that  secrete  an  irritating  liquid  for  pro- 


Amphibia.  193 

tection.  The  toes  are  .webbed,  but  not  so  completely  as  in 
the  frog.  The  hind  limbs  are  less  fully  developed,  and  so 
the  toad  merely  hops,  instead  of  j&mping  like  the  frog. 
The  frog  has  teeth  in  the  upper  *jaw  only,  the  toad  in 
neither  jaw.  The  toad  lives  away  from  the  water ;  still  it 
goes  to  the  water  to  lay  its  eggs,  and  the  young  tadpoles 
pass  through  the  same  stages  of  development  as  the  frog. 
The  toad  lays  its  eggs  in  strings,  while  those  of  the  frog 
are  in  masses.  The  tadpoles  of  the  toad  are  usually 
darker  than  those  of  the  frog.  The  toad  has  the  same 
kind  of  tongue  as  the  frog  and  catches  insects  in  the  same 
way.  The  toad  is  usually  of  a  duller  color,  corresponding 
with  its  surroundings. 

The  tree  toads  or  tree  frogs  are  somewhat  warty  and 
thus  get  the  name  "  toads,"  but  they  are  in  a  different 
family  from  either  frogs  or  toads.  They  are  peculiar  in 
having  the  tips  of  the  ringers  and  toes  dilated  into  disks, 
which  adhere  and  thus  aid  in  climbing.  No  matter  how 
high  and  dry  they  may  live  in  trees,  they  return  to  the 
water  to  lay  their  eggs.  As  is  well  known,  they  can 
change  their  color  through  a  considerable  range,  from 
nearly  white  to  nearly  black,  in  keeping  with  the  surface 
on  which  they  are  resting.  The  hind  limbs  are  elongated 
as  in  other  frogs,  but,  since  they  jump  little,  if  any,  the 
muscles  of  these  limbs  are  slightly  developed,  making 
them  slender  instead  of  strong  and  muscular. 

Though  the  larynx  is  poorly  developed,  nearly  all  the 
frogs  and  toads  have  voices.  The  males  have  louder  voices, 
and  most  of  these  are  well  known,  from  the  faint  "  peep  " 
of  the  little  frogs  and  the  shrill  "  trill "  of  the  tree  toad  to 
the  heavy  bass  notes  of  the  bullfrog. 

Some  Peculiar  Forms  of  Development.  —  In  some  of  the  islands  of 
the  ocean  where  there  are  no  marshes,  the  development  is  direct,  the 


194  Descriptive  Zoology. 

young  being  hatched  in  the  form  of  the  adult.    A  few  forms  bring  forth 
the  young  alive. 

CHARACTERISTICS  OF   AMPHIBIA. 

The  Amphibia  breathe  by  gills  in  the  larval  state,  but 
generally  develop  lungs  in  becoming  adult.  They  have  no 
fin  rays  as  with  the  fishes,  but  usually  have  paired  limbs 
with  distinct  fingers  and  toes. 

Aquatic  Life  vs.  Terrestrial  Life.  —  Several  lines  of  investigation 
converge  to  prove  that  at  one  time  the  globe  was  entirely  covered  by 
water.  Of  course  until  there  was  land  there  could  be  no  land  life. 
What  were  the  first  forms  of  life  on  the  land  ?  Did  some  of  the 
forms  of  aquatic  animals  gradually  become  fitted  for  living  on  land  and 
then  desert  the  water  ? 

The  study  of  the  amphibia  seems  to  throw  some  light  on  these  ques- 
tions. In  the  ganoid  fishes  we  saw  that  the  swim  bladder  had  some  cir- 
culation of  blood  in  its  walls  and  that  there  was  an  opening  from  the. 
gullet  into  the  swim  bladder,  which  is,  in  action  at  least,  a  sort  of  rudi- 
mentary lung.  The  lungfishes  have  the  air  bladder  still  more  com- 
pletely developed  as  a  lung.  The  lungfishes  came  to  the  very  door  of 
land  life,  but  remained  aquatic.  The  Amphibia  boldly  stepped  over  the 
threshold  and  were,  probably,  among  the  first  of  the  animal  kingdom  to 
emerge  from  the  water  to  live  upon  the  land.  This  transition  from  life 
in  the  water  to  life  upon  the  land  marks  a  great  step  upward.  Perhaps  it 
would  be  hard  to  believe  that  any  group  of  animals  had  made  such  a 
profound  change,  if  it  were  not  for  the  fact  that  we  see  this  same  change 
in  the  individual  life  of  every  amphibian. 

Gradation  among  the  Amphibia. —  It  is  interesting  and  instructive  to 
observe  the  successive  progress  in  the  various  groups  of  amphibians. 
If  we  consider  in  succession  the  siren,  mud  puppy,  salamander,  and  frog, 
we  see  that  they  all  have  traveled  along  the  same  road,  only  some  have 
gone  farther  than  others.  They  all  start  as  limbless  tadpoles,  with  gills, 
practically  in  the  same  stage  of  development  as  the  fishes.  The  siren 
develops  one  pair  of  legs,  retains  the  legs  and  gills,  although  developing 
lungs,  and  goes  no  farther.  The  mud  puppy  makes  a  slight  advance 
by  developing  another  pair  of  legs.  It  retains  the  two  pairs  of  legs  and 
the  gills,  at  the  same  time  breathing,  in  part,  by  means  of  lungs.  The 
salamander  takes  a  decided  step  upward  when  it  sheds  the  gills  and 


Amphibia. 


breathes  by  means  of  lungs.  The  frog  goes  through  all  these  stages, 
but  rises  to  a  still  higher  level  by  getting  rid  of  the  tail  which  it  had  in 
its  larval  life.  In  short,  each  of  these  forms  has  gone  through  all  the 
stages  represented  by  the  forms  below  it  in  the  scale,  but  has  discarded 
certain  features  and  has  advanced  to  a  higher  plane  and  leads  a  more 
active  life. 

The  life  history  of  the  frog,  therefore,  serves  to  review  all  the  other 
forms  of  amphibians  below  it  in  the  scale.  The  temporary  stages  of  the 
frog's  life  represent  the  permanent  form  of  the  lower  kinds  of  Amphibia. 
To  put  it  in  another  way,  —  they  all  start  at  the  foot  of  the  same  stairs 
at  the  fish  level,  so  to  speak ;  the  siren  climbs  up  on  the  first  step  and 
stops  there ;  the  mud  puppy  makes  one  more  step  and  rests  content ; 
the  salamander  mounts  still  higher  by  a  step  and  has  reached  its  high- 
est point ;  while  the  frog  takes  all  of  these  steps  and  reaches  out  once 
again  and  tops  the  series  by  getting  on  the  highest  step  of  the  stairs. 

This  series  illustrates  a  law  which,  though  general,  does  not  appear 
so  clear  in  some  other  groups.  The  stages  of  development  of  the 
individuals  of  the  higher  groups  recapitulate  the  development  of  the 
group  as  a  whole;  or,  in  other  words,  "the  development  of  the  individ- 
ual epitomizes  the  development  of  the  race.11 

DIFFERENCES  BETWEEN  FISHES  AND  AMPHIBIANS. 

FISHES.  AMPHIBIANS. 


Persist  through  life Gills    . 

Air  bladder  respiratory  in  lungfishes       .  Lungs 
i  Auricle,  i  Ventricle      ....  Heart  . 


May  disappear  in  adult 

Present  in  adult 

2  Auricles,  i  Ventricle 


Fins  with  fin  rays Limbs 

Scales  (usually)       ....  Exoskeleton 
Not  open  to  mouth  (except  lungfish)         Nostrils 


.    Limbs  with  digits 

Skin  smooth  (usually) 

.    Open  into  mouth 


Class  Amphibia  . 


ORDERS  OF  AMPHIBIA. 

r  Order  i.    Urodela      . 
•    •{  Order  2.    Anura 

I  Order  3.    Gymnophiona 


Salamander 

Frog 

Blind-snake 


CHAPTER   XIII. 
BRANCH   CHORDATA. 

CLASS    REPTILIA. 

THERE  are  four  principal  forms  of  reptiles,  represented 
by  the  lizard,  snake,  turtle,  and  alligator. 

THE   LIZARDS. 

General  Characters  of  Lizards.  —  Lizards  are  scaly  rep- 
tiles, having,  in  the  typical  forms,  two  pairs  of  limbs  and 
an  elongated  body,  with  a  long,  tapering  tail,  frequently 
twice  as  long  as  the  rest  of  the  body.  The  middle  of  each 
vertebra  of  the  tail  has  a  thin  layer  of  cartilage,  at  which 
places  the  tail  easily  breaks  off.  The  advantage  of  this 
arrangement  is  readily  seen.  When  attacked  by  an 
enemy  the  chances  are  the  lizard  will  be  seized  by  the 
tail,  for  he  is  probably  trying  to  escape  by  flight.  The 
brittle  tail  breaks  off,  and  as  this  constitutes  the  greater 
part  of  the  length,  the  pursuer  thinks  he  has  the  main 
part ;  at  any  rate,  while  he  is  holding  this  the  curtailed 
lizard  may  make  good  his  escape.  But  the  tail  grows  out 
again. 

In  capturing  lizards,  which  often  lie  basking  in  the  sun, 
it  is  best  to  creep  stealthily  upon  them  till  within  arm's 
length,  and  quickly  dart  the  hand  forward.  Unfortunately, 
in  thus  grasping  them,  the  tail  is  in  most  cases  broken  off. 

There  are  five  toes,  with  claws,  on  each  foot.  There 
are  no  external  ears,  but  the  tympanum  is  sunken,  leaving 

196 


Reptilia. 


197 


a  depression  back  of  the  eye.  The  eyes  have  movable 
upper  and  lower  lids.  The  teeth  are  attached  to  the  ridge 
or  edge  of  the  jaws,  and  are  not  set  in  sockets. 

Lizards  feed  on  insects,  worms,  and  other  small  animals, 
though  a  few  forms  are  herbivorous. 

Lizards  are  active  in  habits,  some  being  called  "  swifts." 
They  are  found  on  the  ground,  more  often  in  sandy  soils, 
on  rocks,  trees,  walls,  etc., 
being  most  abundant  in 
warm  countries.  There  are 
not  many  north  of  latitude 
40°.  A  few  live  more  or  less 
in  the  water,  but  they  do 
not  have  gills  at  any  stage 
of  their  lives. 

Lizards  lay  eggs  of  com- 
paratively large  size,  which 
are  covered  by  a  tough 
leathery  or  limy  shell. 

Many  lizards  are  bril- 
liantly colored,  and  some 
have  power  to  change  their 
color;  most  noted  of  these 
are  the  chameleon,  of  the 
old  world,  and  the  Anolis 
(Fig.  123),  found  in  the 
Carolinas  and  Florida,  which 
readily  changes  from  a 
bright  green  to  a  dull  brown 


FIG.  123.    GREEN  LIZARD. 

From  Kingsley's  Comparative  Zoology, 


according  to  its  surround- 
ings. Put  one  of  these  fellows  in  a  box  with  a  lot  of  dead 
pine  needles,  and  note  the  color  change.  This  lizard  is 
often  sold  under  the  name  "chameleon." 


198  Descriptive  Zoology. 

The  Chameleon.  —  The  true  chameleon  is  found  in  Africa.  Its  power 
to  change  its  color  has  been  mentioned.  It  has  a  laterally  compressed 
body,  with  a  prehensile  tail.  Its  feet  are  fitted  for  climbing  by  having 
two  toes  on  one  side  and  three  on  the  other.  The  two  eyes  can  move 
independently  of  each  other,  and  the  tongue  can  be  darted  out  four  or 
five  inches  after  insects. 

The  Horned  Toad.  — This  is  a  lizard  with  a  broad,  relatively  short 
body,  with  spines  on  the  back  of  the  head.  It  is  found  in  the  dry 
regions  of  the  Western  and  Southwestern  states. 


FIG.  124.    THE  GILA  MONSTER. 

The  only  poisonous  lizard.  —  From  Kellogg's  Zoology. 

The  "Gila  Monster."  —  This  is  the  largest  of  the  lizards  found  in 
the  United  States,  being  about  eighteen  inches  long.  It  is  found  from 
New  Mexico  south  and  west.  It  is  brown,  with  red  markings.  Its 
bite  is  poisonous,  though  seldom  fatal  to  man. 

The  Iguanas.  —  In  Central  and  South  America  and  the  West  Indies 
are  found  the  lizards  called  iguanas.  They  are  about  three  feet  long, 
and  are  found  on  the  lower  branches  of  trees.  They  are  used  as  a  food 
by  the  natives,  and  are  said  to  be  excellent  eating. 

The  Monitors.  —  The  monitors  are  found  in  Africa,  Australia,  and 
the  East  Indies.  They  are  the  largest  of  living  lizards,  being  five  or 
six  feet  long. 

Differences  between  a  Salamander  and  a  Lizard.  —  Salamanders  are 
commonly  called  lizards.  The  two  animals  have  a  general  resemblance 
in  form,  both  having  elongated  bodies,  with  two  ^  pairs  of  limbs  and  a 
long  tail.  The  following  tabular  statement  shows  important  points  of 
difference :  — 

SALAMANDER  (Amphibian).  LIZARD  (Reptile). 

Smooth Skin Scaly 

Unarmed Toes With  claws 

Present  in  young Gills No  gills  at  any  stage 

A  metamorphosis Development Young  like  adult 


Reptilia.  199 

The  Joint-snake.  —  Every  one  has  heard  of  the  glass-snake  or  joint- 
snake,  which  is  by  no  means  rare  in  the  Central  states.  The  commonly 
accepted  story  is  that  when  struck  it  flies  to  pieces,  and  that  the  pieces 
come  together  again,  making  the  animal  whole  as  before.  The  facts 
are  as  follows :  The  glass  snake  is  a  lizard  without  legs,  and  with  a  tail 
two  or  three  times  as  long  as  the  body  proper;  hence  it  looks  very 
much  like  a  snake.  A  closer  examination  would  show  that  it  can  shut 
its  eyes,  which  no  snake  can  do.  There  is  also  a  depression  marking 
the  ear,  not  found  in  snakes.  A  groove  along  each  side  of  the  body  is 
also  a  feature  never  found  in  snakes.  The  tail  is  very  brittle,  as  in  all 
lizards.  When  struck,  the  tail  is  easily  broken  off  and  broken  into 
several  pieces,  the  short  body  usually  crawling  quickly  away.  No  part 
of  the  tail  lives.  The  disappearance  of  the  pieces  of  the  tail  is  easily 
accounted  for  by  any  one  who  knows  how  many  animals  are  on  the 
lookout  for  something  to  eat.  To  one  who  knows  the  animal's  struc- 
ture an  explanation  is  easy ;  it  is  also  easy  to  comprehend  how  the 
ignorant  usually  accept  the  popular  story.  If  one  can  be  obtained, 
carefully  compare  it  with  a  snake. 

THE   SNAKES. 

Characteristics  of  Snakes.  —  The  absence  of  limbs  is  not 
distinctive,  since  the  glass-snake  is  a  legless  lizard,  and 
some  snakes  have  rudiments  of  hind  limbs.  In  snakes 
there  are  no  movable  eyelids,  the  eyes  being  covered  by 
the  thin,  transparent  epidermis.  The  mouth  is  very  dilat- 
able, the  lower  jaw  being  held  by  extensible  ligaments, 
and  the  two  halves  of  the  lower  jaw  are  also  loosely  con- 
nected so  they  can  be  stretched  apart  during  swallowing. 
The  tongue  is  long,  soft,  cylindric,  and  forked  at  the  tip  ; 
it  serves  as  an  organ  of  touch,  and  has  nothing  to  do  with 
the  poison  apparatus.  The  teeth  are  relatively  small, 
pointed  backward,  and  serve  to  hold  the  prey  and  to  aid  in 
swallowing.  There  is  no  breastbone.  The  number  of 
vertebrae  is  great,  in  the  boa  over  four  hundred.  Ribs 
begin  on  the  second  vertebra  and  continue  the  whole  length 
of  the  body  cavity. 


2OO  Descriptive  Zoology. 

Locomotion  of  Snakes.  — The  chief  mode  of  locomotion  in 
a  sinuous  line  is  so  well  known  that  a  double  curve  is  desig- 
nated as  "  serpentine.  "  It  should  first  be  noted  that  along 
the  whole  length  of  the  ventral  surface  is  a  series  of  broad, 
overlapping  plates,  —  the  scutes  or  ventral  plates.  By 
means  of  these  the  snake  "gets  hold"  of  rough  places,  for 
on  a  perfectly  smooth  surface  it  can  make  no  progress.  By 
the  winding,  wavelike  motion  of  its  body  it  both  pulls 
and  pushes  itself  along.  The  absence  of  limbs  enables  it 
to  glide  through  grass  and  weeds  and  into  crevices  and  holes. 
Snakes  also  glide  along  with  the  body  straight.  This  is 
accomplished  by  rhythmically  drawing  the  ribs  and  scutes 
forward  and  pushing  them  backward,  or,  as  some  express 
it,  by  "walking  on  the  ribs." 

Food  of  Snakes.  — Snakes  are  carnivorous  and  take  only 
living  prey.  This  they  swallow  whole.  The  constrictors 
wind  the  body  around  the  victim  and  crush  it.  Our  com- 
mon black  snake  (blue  racer)  is  a  good  example  of  a  con- 
strictor. Our  commoner  snakes  feed  on  toads,  frogs,  birds, 
etc.  Garter  snakes  sometimes  eat  earthworms.  Water 
snakes  catch  fish,  frogs,  and  other  aquatic  animals. 

Process  of  Swallowing.  —  Birds  are  usually  swallowed  head 
first.  If  the  snake  catches  a  frog  by  a  hind  leg,  that  part 
leads  the  way  in.  The  backward-pointing  teeth  prevent 
escape.  The  two  halves  of  the  lower  jaw  are  alternately 
pushed  forward  and  drawn  backward,  and  the  victim  is 
thus  slowly  drawn  in.  Meanwhile  the  salivary  glands 
lubricate  the  object. 

The  Organs  of  Digestion.  —  The  gullet  is  as  wide  as  the 
mouth,  and  there  is  no  constriction  or  line  of  demarcation 
between  it  and  the  storm rh.  The  posterior  end  of  the 
stomach  is  glandular.  About  halfway  back  in  the  body 


Reptilia. 


201 


cavity  the  stomach  ends 
and  is  continued  into 
the  intestine,  which 
pursues  nearly  a 
straight  course.  Near 
the  posterior  part  of 
the  body  cavity  it 
widens,  forming  the 
cloaca.  Alongside  the 
stomach  is  the  long, 
narrow  liver ;  from  its 
hinder  end  the  bile  duct 
extends  back  to  the  bile 
sac,  and  from  this  a 
duct  empties  into  the 
intestine  a  little  way 
back  of  the  stomach. 
The  pancreas,  a  pale, 
roundish  organ,  also 
pours  its  secretion 
through  a  duct  into  the 
intestine.  Digestion  is  ° 
a  slow  process,  as  might 
be  guessed  from  the 
condition  in  which  the 
food  is  swallowed,  and 
the  snake  lies  stupid 
and  inactive  for  a  long 
time  after  such  a 
"bolted"  meal. 

How  the  Snake 
Breathes.  —  The  right 
lung  is  long  and  nar- 


202  Descriptive  Zoology. 

row,  and  continues  back,  as  a  transparent  air  sac,  through 
most  of  the  length  of  the  body  cavity.  The  left  lung  is 
rudimentary,  sometimes  being  so  small  it  is  difficult  to  see. 
The  windpipe  is  long,  beginning  very  close  to  the  front  of 
the  floor  of  the  mouth.  This  is  regarded  as  an  adaptation 
to  the  mode  of  eating,  so  that  the  snake  may  not  be  suffo- 
cated during  the  long  and  tedious  process  of  swallowing. 

Circulatory  System.  —  The  heart  beat  is  slow  and  the 
circulation  not  very  active.  The  heart  continues  to  beat 
long  after  the  head  is  severed.  The  temperature  of  the 
blood  varies  with  that  of  the  surroundings. 

Excretory  Organs.  —  In  the  posterior  part  of  the  body 
cavity  are  the  two  long,  slender  kidneys,  whose  ducts  open 
into  the  cloaca. 

The  Eggs  and  the  Young.  —  Eggs  are  produced  in  two 
long,  narrow  ovaries;  the  oviducts  also  open  into  the 
cloaca.  Some  snakes  deposit  their  eggs  in  the  earth, 
though  probably  a  majority  bring  forth  the  young  alive. 

Senses  of  Snakes.  —  Sight  and  touch  are  fairly  well  de- 
veloped, though  a  study  of  snakes  does  not  reveal  a  keen 
sense  of  sight.  Some  snakes  are  affected  by  music,  show- 
ing a  sense  of  hearing.  Of  their  senses  of  smell  and  taste 
we  know  but  little. 

Adaptations  of  Internal  Organs  to  External  Form.  —  We 
have  seen  how  the  external  form  is  adapted  to  the  mode  of 
life.  Let  us  now  see  how  the  internal  organs  are  fitted  to 
the  necessarily  long,  narrow  space  allotted  to  them.  In 
the  first  place  the  body  cavity  is  so  long  that  a  moderately 
long  digestive  tube  is  accommodated  without  the  necessity  of 
coiling  it,  as  in  many  animals.  But  one  lung  is  developed, 
and  that  one  is  long  and  narrow,  whereas  our  bodies  admit 
of  two  relatively  wide  lungs  placed  side  by  side.  The  liver 


Reptilia.  203 

is  long  and  slender,  and  its  bile  sac  is  behind  it.  Not  only 
are  the  ovaries  (and  spermaries)  and  kidneys  slender,  but 
they  are  not  directly  opposite  each  other ;  in  short,  every- 
thing is  arranged  on  the  tandem  plan.  Yet  the  snake  is 
bilaterally  symmetrical,  in  its  fundamental  plan,  like  other 
vertebrates  and  the  vast  majority  of  animals. 

Poisonous  Snakes?  —  Some  of  the  front  upper  teeth  of 
these  snakes,  called  "  fangs,  "  are  especially  adapted  for  in- 
troducing poison.  They  are  longer  than  the  other  teeth, 


FIG.  126     DIAMOND  RATTLESNAKE. 

From  photograph  by  W.  H.  Fisher.  —  From  Recreation,  by  permission  of  G.  O.  Shields. 

can  usually  be  erected  or  folded  back,  and  have  a  hollow, 
or  groove,  by  which  poison  passes  from  the  poison  sac  into 
the  wound  by  muscular  pressure  on  the  sac.  The  poison 
gland  is  a  modified  form  of  salivary  gland.  This  poison  is 
not  a  stomach  poison,  but  a  violent  blood  poison.  Our 
chief  poisonous  snakes  are  the  rattlesnake,  now  becoming 
rare  in  all  thickly  settled  regions,  the  copperhead,  and  the 
water  moccasin  of  the  South.  Their  abundance  and  the 
danger  from  them  are  both  grossly  exaggerated.  As  an 


204 


Descriptive  Zoology. 


antidote,  a  hypodermic  injection  of  permanganate  of  potash 
(i  to  100),  is  by  many  now  preferred  to  alcoholic  liquor.    In 
India  the  cobra  kills  several  thousand  persons  yearly. 
(See  The  American  Natural  History.     Hornaday.) 
How  Snakes  protect  Themselves.  —  ( i )    By  their  color, 
(2)  by  flight,  (3)  by  their  odor,  (4)  by  their  poison. 

Many  snakes  are  colored  so  like  their  surroundings  as  to 
be  decidedly  inconspicuous,  and  this  is  of  advantage  both 

in  escaping  enemies  and  in 
securing  their  prey.  By  their 
noiseless  mode  of  locomotion 
they  can,  unobserved,  ap- 
proach a  victim  or  elude  a 
pursuer.  We  are  so  familiar 
with  their  stealthy  move- 
ments that  we  are  not  sur- 
prised when  we  learn  that 
the  words  snake  and  sneak 
are  of  the  same  origin  ; 
nor  do  we  wonder  that  there 
has  been  a  long-standing 
enmity  between  man  and  serpent.  Yet  the  majority  of 
snakes  are  entirely  harmless,  and  are  as  much  surprised  as 
we  are  when  we  "  meet  by  chance."  Many  snakes  have  a 
disagreeable  odor  which  probably  serves  to  protect  them 
from  some  enemies.  Lastly,  the  poisonous  snakes  use  their 
poison  to  secure  food  and  to  protect  themselves.  Among 
the  enemies  of  snakes  are  to  be  reckoned  several  kinds  of 
birds,  such  as  the  shrikes  and  hawks,  hogs,  wild  and  domesti- 
cated, bears  (occasionally),  and  various  other  animals. 

Molting.  —  At  least  once  a  year  snakes  shed  the  epi- 
dermis over  the  entire  body,  even  over  the  eyes.  During 
this  process  they  are  dull-colored  and  inactive. 


FIG.  127. 


DISSECTION  OF 
RATTLESNAKE. 


HEAD  OF 


Showing  fangs  and  poison  sac  ( /).  —  From 
Kingsley's  Comparative  Zoology. 


Reptilia.  205 

DIFFERENCES    BETWEEN   A    SNAKE   AND   A  "GLASS 

SNAKE." 
SNAKE.  GLASS  SNAKE. 

No  lids  ........       Eyes Movable  lids 

Dilatable Mouth Not  dilatable 

Extensible Tongue    .     .    '.     .     .     Not  extensible 

Invisible  externally Ear Visible  externally 

Broad  plates Ventral  scales Small 

Short,  strong Tail Long,  brittle 

Absent Lateral  groove Present 

THE   TURTLES. 

General  Characters  of  Turtles.  —  In  turtles  the  relatively 
short  and  broad  body  is  inclosed  between  two  bony  shields, 
the  dorsal  one  being  called  the  carapace,  and  the  ventral, 
the  plastron.  The  carapace  is  made  up  of  (i)  the  widened 
spines  of  the  thoracic  vertebrae,  (2)  the  ribs,  which  have 
widened  and  grown  together,  and  (3)  a  series  of.  marginal 
plates.  There  is  no  breastbone,  but  the  plastron  is  made 
of  a  set  of  bony  plates.  Both  carapace  and  plastron  are 
covered  by  a  set  of  horny,  epidermal  scales  which  do  not 
coincide  with  the  underlying  bony  plates.  The  "tortoise 
shell "  of  commerce  is  made  of  the  epidermal  plates  of  the 
big  sea  turtle  known  as  the  hawkbill  turtle. 

There  are  no  teeth,  but  instead  the  jaws  are  horny.  The 
neck  and  tail  are  the  only  movable  parts  of  the  spinal 
column,  and  these,  with  the  legs,  can  be  withdrawn  so  as 
to  be  protected  by  the  shell.  In  the  boxshell  turtle  there 
is  a  hinge  in  the  plastron  to  make  the  protection  more 
complete  by  closing  the  shell.  The  sea  turtles  have  pad- 
dles, while  the  land  turtles  have  feet,  with  more  or  less 
distinct  toes.  Some  of  the  sea  turtles  weigh  as  high  as  a 
thousand  pounds.  The  green  turtles,  so  valued  for  soup, 
are  caught  in  the  West  Indies  at  night,  when  they  come 


206  Descriptive  Zoology. 

ashore  to  lay  their  eggs.  Among  the  more  noticeable  of 
our  inland  turtles  are  the  fierce  snapping  turtle,  the  soft- 
shell  turtle,  and  the  "  gopher  "  of  the  South,  which  burrows 
in  the  ground.  The  terrapins  of  Chesapeake  Bay  are 
noted  for  their  quality  as  food.  All  turtles  bury  their  eggs, 
and  our  northern  forms  all  hibernate  in  the  mud. 

THE  ALLIGATORS. 

General  Features.  —  The  alligators  and  crocodiles  are 
like  lizards  in  general  form,  but  differ  from  them  in  several 
important  points.  They  swim  well  by  means  of  the  verti- 
cally flattened  tail.  The  skin  is  covered  with  horny 
scales,  those  of  the  back  having  corresponding  underlying 
bony  plates.  The  teeth  of  alligators  are  set  in  sockets, 
which  is  true  of  no  animals  below  it  in  scale.  The  heart 
is  also  more  complete  than  in  the  other  reptiles,  having  a 
complete  partition  separating  the  ventricle  into  two  parts. 
The  temperature  is  about  that  of  the  surrounding  air  or 
water.  The  brain,  though  more  highly  developed  than  in 
other  reptiles,  is  small  relative  to  the  size  of  the  body  and 
the  skull.  The  alligators  have  a  muscular,  gizzardlike 
stomach.  The  young  feed  on  fishes  and  small  animals, 
but  the  full-grown  alligators  seize  mammals,  for  which  they 
lie  in  wait  at  the  edge  of  the  water  until  the  animals  come 
down  to  drink  or  swim.  The  nostrils,  eyes,  and  ears  are 
at  the  top  of  the  head,  so  these  reptiles  can  lie  concealed, 
with  their  main  sense  organs  extending  into  the  air  to 
discover  their  prey ;  they  very  much  resemble  a  stranded 
log.  The  nostrils  can  be  closed  by  a  valve,  which  is 
done  when  a  victim  is  dragged  under  water  to  drown. 
Alligators  dig  holes  in  the  banks,  in  which  they  lay  their 
eggs,  which  are  sometimes  as  large  as  those  of  a  goose. 

The  alligators  of  our  Southern  states  grow  to  a  length  of 


Reptilia.  207 

ten  or  twelve  feet.  Alligators  are  confined  to  the  western 
hemisphere,  occurring  in  the  Southern  states,  Central  and 
South  America. 

Crocodiles  are  found  in  both  the  old  world  and  the 
new.  One  species  is  found  in  southern  Florida. 

Extinct  Reptiles.  —  In  earlier  geologic  ages  reptiles  were  very  much 
more  numerous  than  at  present.  Not  only  were  they  more  abundant, 
but  there  were  more  kinds ;  and  many  of  them  were  large,  some  being 
eighty  feet  in  length.  Some  were  lizardlike,  with  long,  slender  necks. 
Others  were  fishlike.  Some  had  resemblances  to  birds.  The  tracks  of 
many  of  these  ancient  reptiles  in  the  mud  have  hardened  into  rock,  and 
have  often  been  called  "  fossil  bird  tracks.'1  Perhaps  the  most  remark- 
able were  the  flying  reptiles.  They  are  supposed  to  have  been  rather 
batlike  in  appearance.  The  remains  of  these  reptiles  are  found  in  rocks 
in  many  parts  of  the  world,  and  the  age  in  which  they  were  most  preva- 
lent is  called  by  geologists  the  "  Age  of  Reptiles." 

General  Characteristics  of  Reptilia.  —  Reptiles  are  cold- 
blooded vertebrates,  covered  with  scales,  and  when  toes 
are  present  they  end  in  claws.  There  is  no  metamorphosis 
after  leaving  the  egg.  There  are  no  gills  at  any  stage  of 
life.  Reptiles  produce  large  eggs  which  are  covered  by  a 
tough  limy  or  leathery  shell.  Some  reptiles  are  ovo- 
viviparous.  Reptiles  show  a  decided  advance  beyond 
amphibians  in  the  development  of  the  nervous  system ; 
in  the  respiratory  system,  since  they  breathe  by  lungs 
after  leaving  the  egg ;  and  in  the  circulatory  system,  the 
heart  of  the  alligator  having  four  cavities,  as  in  birds  and 
mammals. 

CLASSIFICATION    OF    REPTILIA. 

f  Lacertilia  —  lizards. 

{Order  i.  Squamata.  j  „    .....  . 

(Ophidia  —  snakes. 
Order  2.    Chelonia  —  turtles. 
Order  3.    Crocodilia  —  alligators. 


CHAPTER    XIV. 
BRANCH   CHORDATA. 

CLASS   AVES. 
Example.  —  The  Common  Pigeon. 

Adaptation  for  Flight.  —  The  pigeon  is  fitted  for  flying : 
(i)  by  the  wings,  which,  with  their  wide,  strong,  yet  elastic 
feathers,  are  air  paddles  of  marvellous  efficiency ;  (2)  by 
the  powerful  breast  muscles  which  move  the  wings;  (3) 
by  the  lightness  of  the  skeleton  ;  (4)  by  the  air  sacs  through- 
out the  body,  which  render  it  more  buoyant;  (5)  and,  not 
least,  by  the  shape,  -being  double  pointed,  so  as  to  penetrate 
the  air  with  the  least  resistance. 

Structure  of  a  Feather.  —  Let  us  consider  the  structure  of 
one  of  the  quill  feathers.  It  consists  primarily  of  two  parts, 
the  shaft  and  the  vane,  or  flattened  part.  The  shaft  is  solid 
so  far  as  the  vane  extends,  but  the  basal  part  is  hollow,  and 
is  called  the  quill.  The  two  sides  of  the  vane  are  unequal 
in  width,  and  the  feathers  overlap  so  that  the  wider  side  of 
the  vane  is  beneath.  The  vane  is  made  up  of  side  branches 
called  barbs,  arranged  in  a  close  row.  From  each  side  of 
each  barb  arise  secondary  branches,  called  barbules ;  and 
the  barbules  of  adjacent  barbs  interlock  by  little  hooked 
ends,  so  that  the  whole  vane  is  firm. 

Feathers  are  developed  from  papillae  of  the  skin.  In  a 
growing  feather  it  can  be  seen  that  the  quill  is  full  of  pulp 
supplied  with  blood.  In  the  fully  developed  feather  the 

208 


Aves.  209 

dry,  pithy  remains  of  this  pulp  are  found  in  the  quill,  which 
is  now  narrowed  at  the  base,  but  still  shows  an  aperture. 

Kinds  of  Feathers.  —  There  are  four  principal  kinds 
of  feathers :  ( I )  The  quills  found  on  the  wings  and  tail. 
(2)  The  contour  feathers,  which  have  the  same  general 
structure  as  the  quills,  but  are  smaller,  and  lie  close  to 
the  body.  They  protect  the  body  from  bruises,  and  also 
from  cold,  being  the  very  best  of  non-conductors  of  heat. 
Their  mode  of  overlapping  serves  admirably  for  shedding 
rain  and  for  retaining  the  heat  when  flying  through  cold 
air.  (3)  Downy  feathers,  which  differ  from  the  above  , in 
not  having  the  barbs  fastened  together  by  hooked  barbules ; 
the  result  is  a  loose,  soft  feather,  well  suited  for  retaining 
heat.  These  feathers,  when  present,  are  inside  the  contour 
feathers,  where  we  should  expect  to  find  them.  The  young 
pigeon  has  downy  feathers,  but  they  disappear  in  the  adult. 
(4)  The  pinfeathers  are  fine,  hairlike  feathers,  usually  left 
after  the  pigeon  is  plucked,  and  usually  removed  from  fowls 
by  singeing.  They  show  that  they  are  feathers  by  a  little 
tuft  of  barbs  at  the  tip. 

Distribution  of  Feathers.  —  Feathers  are  not  evenly  dis- 
tributed over  the  surface  of  the  body  ;  but  there  are  certain 
areas  from  which  they  grow,  and  certain  other  areas  from 
which  feathers  never  grow.  By  separating  the  feathers  on 
a  bird's  breast  it  may  readily  be  seen  that  no  feathers  de- 
velop there.  There  are  also  bare  places  on  the  sides  of  the 
neck  and  in  other  places ;  but  the  length  of  the  feathers 
and  their  mode  of  overlapping  cover  these  bare  spots,  so 
that  most  people  hardly  know  of  their  existence. 

The  Pigeon's  Wing.  —  The  wing,  like  our  arm,  consists  of 
three  parts,  the  arm,  forearm,  and  hand.  The  similarity 
of  the  first  and  second  of  these  to  the  corresponding  part 
of  our  arms  is  so  evident  that  it  needs  no  explanation.  The 


Descriptive  Zoology. 


sui. 


FIG.  128.  EXTERNAL  FEATURES  OF  A  BIRD. 

From  Kellogg's  Zoology. 


Aves.  2 1 1 

front  angle  of  the  wing,  or  "  bend  of  the  wing,"  as  it  is 
called,  corresponds  to  our  wrist ;  but  the  hand  is  sharply 
bent  back  upon  the  forearm  when  the  wing  is  folded,  a  posi- 
tion we  cannot  assume.  When  the  wing  is  folded,  the  arm, 
forearm,  and  hand  lie  alongside  of  each  other  like  this,  z. 
Further,  the  hand  is  reduced  to  two  fingers,  bound  together, 
and  the  thumb,  which  every  one  has  seen  in  the  plucked 
fowl.  The  thumb,  with  its  feathers,  is  called  the  false  wing. 
The  feathers  borne  on  the  hand  are  called  primaries,  and 
those  supported  by  the  forearm  are  the  secondaries.  In 
some  cases  a  few  of  the  inner  feathers  of  the  forearm  are 
called  tertiaries.  The  wing  is  concave  on  the  inside,  mak- 
ing it  fit  the  body  closely  when  the  wing  is  folded. 

The  Flying  Muscles.  —  To  use  such  a  wing  effectively  as 
an  air  paddle,  it  is  evident  that  there  must  be  very  strong 
muscles.  These  we  find  in  the  breast.  The  bulk  of  the 
breast  is  made  up  of  two  powerful  muscles,  which  cover 
nearly  the  whole  of  the  ventral  surface  of  the  body.  To 
support  these  large  muscles,  and  supply  a  basis  for  their 
attachment  so  they  can  work,  it  is  equally  clear  that  a  con- 
siderable extent  of  bone  is  also  a  necessity ;  hence  the  large 
breastbone.  Not  only  is  the  breastbone  very  large,  but 
along  its  middle  line  is  a  high  ridge,  the  keel.  Lying 
between  the  body  of  the  breastbone  and  the  keel,  and 
attached  to  both,  there  is  on  each  side  the  large  pectoral 
muscle,  the  two  together  constituting  about  one  fifth  of  the 
entire  weight  of  the  body.  At  the  anterior  end,  each  pec- 
toral muscle  narrows  into  a  tendon,  which  is  attached  (in- 
serted) to  the  bone  of  the  upper  arm  (humerus).  By  the 
shortening  of  this  muscle  the  wing  is  pulled  downward. 
Two  points  must  now  be  kept  in  mind:  (i)  the  wing  is 
concave  beneath,  which  enables  it  to  "  catch "  the  air ; 
(2)  the  wider  side  of  the  vane  of  each  quill  is  on  the  under 

^^r»TJ 

- 


212  Descriptive  Zoology. 

side,  so  when  the  wing  is  struck  against  the  air,  the  resist 
ance  presses  the  vanes  together  in  one  continuous  layer, 
through  which  the  air  cannot  pass.  The  result  is  that  a 
strong  "  push  "  is  made  against  the  air,  and  by  reaction  the 
bird  is  propelled  upward  or  forward  according  to  the  direc- 
tion of  the  wing  stroke.  In  seeking  the  muscle  that  raises 
the  wing,  one  would  naturally  look  on  the  dorsal  surface  in 
the  region  of  the  shoulder  ;  but,  oddly  enough,  the  muscles 
that  raise  the  wings  are  also  on  the  breast.  Every  one  has 
noticed  in  the  well-cooked  breast  of  a  bird  that  the  meat  of 
the  breast  separates  into  two  parts,  the  outer  part  being 
large  and  flat,  the  pectoral  muscle  just  described.  Inside 
of  this,  lying  in  the  angle  between  the  body  of  the  breast- 
bone and  the  keel,  is  a  slender  muscle,  somewhat  triangu- 
lar in  cross  section.  This  is  the  subclavian  muscle.  At 
its  anterior  end  it  narrows  into  a  tendon,  which  passes 
up  through  a  hole  left  between  the  bones  that  make  the 
shoulder;  the  tendon  then  turns  and  is  attached  to  the 
upper  (dorsal)  surface  of  the  arm  bone  (humerus).  When 
the  subclavian  muscle  shortens,  this  tendon  acts  as  a  pulley, 
and  elevates  the  wing.  In  raising  the  wing  it  is  desirable 
that  there  should  be  as  little  resistance  as  possible.  This 
condition  is  secured  ( i )  by  the  convex  outer  surface  of  the 
wing;  (2)  by  the  fact  that  pressure  on  the  outside  of  the 
wing  separates  the  quills  and  allows  the  air  to  pass  through 
with  very  little  resistance. 

The  Legs  and  Feet.  —  The  pigeon  is  a  model  flier.  It 
uses  the  feet  but  little,  hence  the  legs  and  feet  are  small 
and  weak.  Heavy  legs  and  feet  would  be  to  the  pigeon  a 
useless  burden.  The  hind  limb  consists  of  three  parts, 
thigh,  leg,  and  foot.  The  true  heel  is  some  distance  from 
the  toes,  where  we  cut  off  the  foot  in  dressing  a  bird.  The 
part  between  the  toes  and  the  heel,  usually  covered  with 


Aves.  213 

scales,  is  the  tarsus.  The  pigeon  has  four  toes,  one  extend- 
ing backward  and  having  two  joints.  Of  the  three  front 
toes,  the  inner  has  three  joints,  the  middle  four,  and  the 
outer  five.  Each  toe  ends  in  a  claw. 

It  should  be  noted  that  the  hip  joints  are  not  only  far 
apart,  but  are  very  high  on  the  body,  being  near  the  dorsal 
surface.  This  enables  the  body  of  the  bird  to  swing  be- 
tween its  two  points  of  support,  somewhat  like  an  ice- 
pitcher  on  its  two  pivots.  Since  the  bird  is  obliged  to  put 
its  head  to  the  ground  so  frequently,  the  convenience  of  this 
arrangement  is  apparent.  When  we  stoop  we  realize  that 
we  are  awkwardly  built  for  soich  a  position.  It  would  at 
first  seem  that  the  bird's  center  of  gravity  is  too  far  forward, 
but  the  length  of  the  toes  must  be  taken  into  account. 

Perching.  —  It  is  to  be  noticed  that  when  a  bird's  leg  is 
drawn  up  close  to  its  body,  the  toes  are  clenched  at  the 
same  time.  This  is  due  to  the  action  of  a  tendon  that 
passes  over  the  joints  of  the  leg  in  such  a  way  that  when 
the  limb  is  bent  the  tendon  is  put  on  a  strain  and  thus  the 
toes  are  flexed.  So  when  the  bird  settles  on  its  perch  the 
toes  grasp  the  perch  without  active  muscular  effort ;  this 
helps  answer  the  question,  "  How  does  a  bird  stay  securely 
on  its  perch  when  asleep?"  There  are  also  muscles  by 
which  the  bird  can  voluntarily  clutch  without  depending  on 
this  purely  mechanical  arrangement. 

The  Pigeon's  Shoulder  Braces.  —  With  such  strong  pull- 
ing as  the  breast  muscles  give  the  wing,  it  will  be  seen  that 
the  shoulder  needs  to  be  firmly  braced,  especially  against 
the  strong  pull  of  the  pectoral  in  making  the  down  stroke 
of  the  wing.  In  the  first  place,  the  shoulder  is  braced 
like  our  own  by  the  collar  bones,  or  clavicles,  the  two  collar 
bones  uniting  near  their  attachment  to  the  anterior  end  of 
the  keel,  together  making  the  "wishbone."  In  addition 


214  Descriptive  Zoology. 

to  this  brace  there  is  an  additional  bone  alongside  of  each 
half  of  the  wishbone,  the  coracoid  bone,  much  stronger 
than  the  collar  bone  itself.  On  the  back  the  shoulder  is 
braced  by  the  strong,  curved  shoulder  blade. 

To  strengthen  the  body  for  the  work  of  flying,  the  verte- 
brae of  the  trunk  are  consolidated,  the  only  parts  of  the 
spinal  column  that  are  flexible  being  the  neck  and  the  tail. 
The  Head  and  Neck.  —  In  many  birds  the  beak  is  the  only 
organ  capable  of  being  used  for  grasping,  hence  the  long, 
flexible  neck,  which  makes  up  for  the  above-mentioned 
stiffness  of  the  trunk.  The  bird  must  be  able  to  reach  the 
ground,  hence  the  length  of  the  neck  is  proportioned  to 
that  of  the  legs ;  the  head  must  also  be  able  to  reach  any 
part  of  the  body.  Some  birds  have  as  many  as  twenty- 
four  cervical  vertebrae.  In  many  birds  the  head  must  be 
darted  forward  quickly  to  secure  prey  or  in  defense.  The 
horny  beak  is  strong,  yet  light,  and  serves  as  a  hand  in 
picking  up  small  objects.  Because  of  the  quick  motion  of 
a  bird's  head,  as  it  picks  objects  out  of  the  dirt,  soft  lips 
would  be  too  delicate.  A  head  that  requires  such  quick 
handling  needs  to  be  light ;  and  in  keeping  with  this  re- 
quirement there  is  an  entire  absence  of  teeth  in  all  exist- 
ing birds,  though  in  a  few  cases  rudiments  of  teeth  are 
found  in  the  embryo.  In  the  plucked  bird  it  is  found  that 
the  neck  is  more  slender  than  would  appear  from  the  out- 
side, the  feathers  filling  the  angle  between  the  neck  and 
the  body,  and  making  on  the  exterior  a  gradual  transition, 
where  in  the  bare  bird  there  is  an  abrupt  change. 

The  Pigeon's  Food  and  Digestive  System.  —  Pigeons  feed 
chiefly  on  grains  and  other  seeds.  These  are  swallowed 
whole,  and  pass  into  the  crop,  an  enlargement  of  the  gullet 
situated  in  tront  of  the  breast.  Here  seeds  are  moistened 
and  well  soaked  before  they  go  farther.  The  crop  serves 


Aves. 


215 


as  a  storing  sac  during  the  hasty  gathering  of  food.  In- 
side of  the  body  cavity  is  the  stomach,  which  consists  of 
two  very  distinct  parts ;  the  first  part  is  the  glandular 
stomach,  or  proventriculus,  and  the  second  is  known  as  the 
gizzard.  The  gizzard  is  very  strong,  having  thick  muscular 
walls.  In  it  the  seeds,  only  partially  softened,  are  to  be 
ground.  To  aid  this  process  small  pebbles  are  swallowed. 
It  is  clear,  therefore,  that  its  inner  wall  needs  to  be  tough ; 


FIG.  129.    INTERNAL  ANATOMY  OF  A  PIGEON. 

it  will  not  do  to  have  the  soft  glands  here,  hence  they  are 
placed  out  of  the  way,  a  little  higher  up  the  digestive  tube 
where  the  secretion  can  trickle  down  upon  the  food  in  the 
grinding  stomach.  The  intestine  arises  from  the  gizzard ; 
first  there  is  a  long  loop,  the  duodenum,  in  which  lies  the 
pancreas.  Its  secretion  is  poured  into  the  duodenum. 
The  liver  is  adjacent  and  the  bile  duct  also  empties  into  the 
duodenum.  The  transition  from  the  small  intestine  to  the 
large  intestine  is  marked  by  two  small,  blind  side  branches, 


2i6  Descriptive  Zoology. 

the  ceca.  The  terminal  portion  of  the  digestive  tube  is 
widened,  and  is  called  the  cloaca.  It  receives  three  sets  of 
products,  (i)  the  residue  of  digestion,  (2)  the  eggs,  and 
(3)  the  excretion  of  the  kidneys. 

The  Circulatory  System  of  the  Pigeon. — The  circula- 
tion of  blood  is  very  rapid  in  birds  because  of  their  great 
activity.  The  heart  is  proportionally  large ;  it  is  com- 
pletely divided  into  two  halves,  so  that  the  blood  moves 
through  one  half  of  the  heart  from  the  lungs  to  the  body, 
and  through  the  other  half  from  the  body  to  the  lungs, 
being  pumped  twice  in  the  circuit  instead  of  once  as  in 
fishes.  An  important  point  to  note  is  that  the  aorta  turns 
to  the  right  instead  of  to  the  left  as  in  our  bodies. 

How  the  Pigeon  Breathes.  —  Respiration  is  exceedingly 
active  in  a  bird.  Imagine  yourself  taking  such  violent  ex- 
ercise as  that  required  for  a  bird  tq  fly  through  the  air  at 
the  rate  of  a  mile  a  minute.  Would  you  not  be  "out  of 
breath"?  The  bird's  lungs  are  of  fair  size;  in  addition 
there  are  air  sacs  in  all  parts  of  the  body,  communicating 
with  the  lungs,  the  bronchial  tubes  continuing  on  through 
the  lungs  into  these  sacs.  The  lungs  do  not  lie  free  in  the 
body  cavity  as  in  our  bodies,  but  are  attached  to  the  dorsal 
wall,  fitting  closely  between  the  ribs.  The  air  sacs  are  also 
in  communication  with  the  hollows  of  the  bones,  which 
adds  to  the  buoyancy.  The  temperature  of  birds  is  higher 
than  that  of  any  other  animals,  being  about  110°  F. 

The  movements  of  respiration  in  birds  is  peculiar,  in  that 
expiration  is  accomplished  by  active  muscular  effort,  and 
inspiration  by  elastic  reaction, —just  the  opposite  of  the 
processes  of  our  bodies. 

The  Excretory  System  of  the  Pigeon.  — The  lungs  serve 
as  organs  of  excretion,  throwing  off  carbon  dioxid.  The 


Aves.  217 

kidneys  are  paired  organs,  lying  embedded  in  the  hollow  of 
the  pelvis,  each  kidney  being  in  three  sections. 

The  Oil  Gland.  —  On  the  rump,  at  the  base  of  the  tail,  is 
the  conical  oil  gland.  It  is  concealed  by  feathers,  but 
when  the  bird  wishes  to  oil  the  feathers,  oil  is  taken  from 
the  gland  by  the  beak  and  spread  over  them.  The  oil 
glands  are  the  only  skin  glands  possessed  by  the  bird, 
there  being  no  glands  distributed  over  the  skin  as  in  many 
other  animals. 

Nervous  System  of  the  Pigeon.  —  The  brain  is  relatively 
large.  It  is  also  wide  in  proportion  to  its  length  as  com- 
pared with  the  brains  of  reptiles  and  amphibians.  The 
anterior  part  of  the  brain  consists  of  the  two  cerebral  hemi- 
spheres (see  Fig.  167).  Back  of  these,  in  the  middle 
line,  is  the  rather  large  cerebellum,  marked  by  transverse 
grooves.  On  the  sides  of  the  cerebellum  are  the  two 
optic  lobes.  The  whole  nervous  system  is  relatively  large, 
the  brain  and  spinal  cord  in  some  of  the  smaller  birds 
constituting  a  greater  proportion  of  the  weight  than  in  any 
other  animals. 

The  Senses  of  the  Pigeon.  —  Sight  is  the  most  highly 
developed  of  the  bird's  senses.  The  eye  is  very  large  in 
proportion  to  the  size  of  the  head.  The  outer  coat 
(sclerotic)  of  the  eye  is  strengthened  by  stiff  sclerotic 
plates.  The  sense  of  sight  is  keen,  enabling  the  bird  to 
discover  food  and  to  escape  enemies. 

The  sense  of  hearing  is  acute,  the  inner  ear  being  well 
developed.  There  is  no  outer  ear,  but  the  depression  lead- 
ing to  the  tympanum  is  easily  to  be  found  back  of  the 
eye,  though  usually  more  or  less  concealed  by  feathers.  The 
sense  of  touch  is  general  over  the  body.  Taste  is  appar- 
ently not  very  acute.  While  it  is  pretty  generally  believed 
that  birds,  especially  carrion  eaters,  have  a  keen  sense  of 


2i 8  Descriptive  Zoology. 

smell,  yet  experiment  seems  to  show  that  this  is  not  so 
acute  as  supposed. 

The  Pigeon's  Voice.  —  The  cooing  of  the  pigeon  is  pro- 
duced by  air  vibrations  made  in  the  windpipe,  but  not,  as 
in  most  animals  with  a  true  voice,  in  a  larynx  at  the  upper 
part  of  the  windpipe.  In  birds  the  organ  of  the  voice  is  at 
the  lower  end  of  the  windpipe,  where  it  forks  to  form  the 
two  bronchi ;  and  it  is  called  a  syrinx  instead  of  a  larynx. 
The  bird  uses  the  voice  to  utter  cries  of  warning,  to  call 
the  young,  and  to  attract  attention  in  the  mating  season. 
It  is  worthy  of  notice  that  the  sweetest  singers  are  not  to 
be  found  among  the  highly  colored  birds,  but  among  those 
of  more  subdued  tints. 

Origin  of  the  Domesticated  Pigeon.  —  All  other  varieties 
of  domesticated  pigeons  appear  to  have  descended  from 
the  rock  pigeon  of  the  old  world.  By  carefully  selecting 
pigeons  having  certain  peculiarities,  and  breeding  from 
these  to  the  exclusion  of  other  forms,  in  time  we  have 
produced  a  large  number  of  varieties  of  pigeons,  known  as 
carriers,  pouters,  fantails,  etc.  This  production  of  vari- 
eties by  interfering  with  the  natural  selection  of  mates  is 
known  as  artificial  selection. 

A  Bird's  Egg.  —  Birds'  eggs  are  proportionately  large. 
This  might  naturally  be  expected,  since  there  is  deposited 
within  the  egg  sufficient  nourishment  to  form  the  chick  in 
resemblance  to  the  adult.  The  eggs  are  formed  in  the 
ovary,  and  it  is  interesting  to  find  that  but  one  ovary  (the 
.left)  is  developed,  though  the  right  ovary  is  represented  by 
a  rudiment.  The  eggs  as  produced  by  the  ovary  consist 
simply  of  the  yolk.  On  one  side  of  the  yolk  is  the  germ 
spot.  As  the  yolk,  which  is  the  real  egg,  passes  along  the 
oviduct,  it  has  added  to  it  first  an  enveloping  mass  of 
transparent  substance  which  is  termed  the  "  white  of  the 


Aves.  219 

egg,"  or  albumen.  The  word  "albumen"  (from  album, 
white)  now  stands  for  the  class  of  substances  having  the 
same  essential  composition  as  the  clear  part  of  the  egg. 
After  the  albumen  is  added  to  the  yolk,  the  oviduct  secretes 
a  limy  shell  which  completes  the  egg.  The  eggs  pass  from 
the  oviduct  through  the  cloaca  on  their  way  out. 

Incubation.  —  Most  birds  incubate  the  eggs.  They  are 
sometimes  laid  on  the  bare  ground,  but  generally  in  a  more 
or  less  carefully  prepared  nest.  These  nests  vary  from  a 
simple  platform  of  sticks  to  the  elaborate  hanging  nest  of 
the  oriole,  woven  of  grass  and  soft  fibers,  or  the  still  more 
ingenious  nest  of  the  tailor  bird.  It  is  to  be  noted  that  the 
nest  is  "  simply  a  cradle  and  not  a  home." 

The  germ  spot  always  turns  uppermost,  so  that  the 
developing  embryo  gets  the  heat  from  the  body  of  the 
incubating  bird.  During  incubation  there  is  an  increase 
in  the  amount  of  blood  circulating  in  the  area  in  contact 
with  the  eggs,  a  provision  for  affording  heat  to  them. 

The  Colors  of  Birds.  —  The  colors  of  feathers  are  due  to 
two  factors,  first  to  certain  coloring  matters,  or  pigments, 
and  second  to  the  structure  of  the  feather,  most  of  the 
luster  and  iridescence  being  due  to  the  latter.  As  a  class 
birds  are  highly  ornamented.  The  males  are  usually  more 
highly  ornamented  than  the  females.  Perhaps  this  is 
because  the  females  are  safer,  during  incubation,  with  dull 
colors.  But  in  many  families  the  sexes  are  colored  alike. 
The  young  generally  resemble  the  adult  female. 

Molting.  —  Birds  shed  their  feathers  and  renew  them  at 
least  once  a  year.  If  the  molting  takes  place  but  once  a 
year,  it  is  usually  in  the  fall,  but  some  birds  also  renew 
their  plumage  in  the  spring.  In  rare  cases  there  is  a  third 
molt.  Most  birds  shed  their  wing  quills  in  pairs,  succes- 
sively, so  that  they  are  at  no  time  deprived  of  the  use  of 


22O  Descriptive  Zoology. 

the  wings  ;  but  the  ducks  shed  their  wing  quills  all  at  once 
and  for  a  time  are  unable  to  fly.  Some  birds  shed  the 
claws,  and  the  puffin  sheds  the  outer  covering  of  the  beak. 

Migration  of  Birds.  —  Comparatively  few  of  the  birds 
that  we  see  during  the  year  reside  with  us  permanently. 
If  one  makes  a  list  of  the  birds  that  remain  through  the 
winter,  he  misses  many  of  his  summer  acquaintances.  The 
crow,  jay,  nuthatch,  chickadee,  some  of  the  woodpeckers, 
several  sparrows,  the  hawks  and  owls,  and  a  few  others 
are  left,  when  the  rest  have  flown  southward.  Why  do 
they  go  ?  The  common  answer  is,  "  Because  they  cannot 
endure  the  cold."  But  if  one  examines  the  feathers  he 
finds  little  difference  between  the  robin  and  the  jay,  or  the 
bluebird  and  the  sparrow.  It  is  chiefly  a  question  of  food. 
The  robin  and  the  bluebird  live  mostly  on  insects  and 
worms.  As  winter  approaches  these  birds  can  no  longer 
find  this  sort  of  food  in  northern  latitudes,  and  they  seek 
a  warmer  climate,  not  so  much  because  they  cannot  stand 
the  cold  as  because  insects  and  worms  cannot  stand  the 
cold.  Woodpeckers  are  insectivorous,  yet  remain ;  but 
they  can  get  the  larvae  from  the  trees  about  as  well  dur- 
ing the  winter  as  in  the  summer.  The  large  majority  of 
the  birds  that  remain  with  us  during  the  winter  are  either 
seed-eating  birds,  like  the  grouse  and  sparrows,  or  car- 
nivorous, as  the  hawks  and  owls.  Some  are  omnivorous, 
like  the  crows  and  jays.  Some  birds,  such  as  the  swal- 
lows, are  very  regular  in  the  times  of  their  migrations. 
Others  are  irregular,  and  some  birds  migrate  or  not, 
according  to  varying  conditions.  We  must  keep  in  mind 
the  bird's  marvelous  power  of  flight ;  in  a  short  time  he 
can  cover  a  very  great  distance. 

Parasitic  Birds.  —  Perhaps  the  most  common  example 
of  the  parasitic  habit  is  seen  in  the  common  cowbird. 


Aves.  221 

It  lays  its  eggs  in  the  nests  of  smaller  birds.  The  eggs, 
being  larger  than  those  of  the  owner  of  the  nest,  receive 
the  most  heat,  and  are  likely  to  hatch  first  and  prevent  the 
development  of  the  rightful  heirs ;  thus  the  usurper  suc- 
ceeds. Our  cuckoo  builds  its  own  nest  and  should  not  be 
confused  with  the  English  cuckoo,  whose  bad  reputation  is 
sometimes  transferred  to  his  American  namesake. 


CHAPTER   XV. 
BRANCH   CHORDATA. 

CLASSIFICATION   OF   AVES. 

EXISTING  birds  are  divided  into  two  great  groups.  All 
flying  birds  have  the  keeled  breastbone,  and  from  this  fact 
of  structure  are  placed  together  in  the  division  Carinatae, 
meaning  "  keeled."  The  ostrich  has  no  keel  on  the  breast- 
bone, hence  is  placed  in  the  division  Ratitae,  from  a  word 
meaning  "  raftlike,"  referring  to  the  shape  of  its  breastbone. 

DIVISION  I.  — RATITAE. 

The  best-known  representative  of  this  division  is  the 
African  ostrich.  It  cannot  fly,  the  wings  being  small ;  but 
it  is  a  swift  runner,  equaling  a  horse  in  speed.  The  breast- 
bone is  not  only  without  a  keel,  but  is  relatively  very  small, 
as  might  be  expected  since  there  are  no  large  flying 
muscles.  The  feathers  on  the  wings  and  tail  have  no 
booklets  on  the  barbules ;  the  result  is  a  plume  instead  of 
a  firm  vane  as  in  the  flying  birds.  These  plumes  have 
been  valued  as  ornaments  from  the  earliest  time,  and  now 
the  rearing  of  ostriches  for  the  plumes  is  an  important 
industry  in  South  Africa  and  southern  California. 

The  ostrich  is  also  noteworthy  from  its  size,  being  the 
largest  of  existing  birds,  standing  from  six  to  eight  feet 
high.  It  has  but  two  toes  on  each  foot.  In  the  same 
division  are  also  the  South  American  ostrich,  the  emu 
of  Australia,  the  cassowary  of  Australia  and  the  East 
Indies.  The  kiwi  of  New  Zealand  has  bristlelike  feathers, 


Aves. 


223 


so  that  it  appears  to  be  covered  with  hair,  and  the  nos- 
trils open  at  the  tip  of  the  long  beak.  The  Ratitae  are 
"  overgrown  degenerate  birds  that  were  once  on  the  right 
road  for  becoming  flying  fowl,  but  through  greediness  and 


FIG.  130.    SOUTH  AMERICAN  OSTRICH. 

From  Kingsley's  Zoology. 

idleness  never  reached  the  'goal/  went  back,  indeed,  and  lost 
their  sternal  keel,  and  almost  lost  their  unexercised  wings" 
(Parker). 

DIVISION   II.— 


This  division  includes  all  flying  birds.     All  of  the  birds 
in  this  part  of  the  world  are  carinate.     The  breastbone 


224 


Descriptive  Zoology. 


is  large  and  keeled  to  support  the  flying  muscles.  The 
barbules  have  booklets  which  unite  the  barbs,  forming  a 
firm  vane.  The  Carinatae  are  divided  into  a  number  of 
orders. 

The  Diving  Birds.  —  The  diving  birds  have  webbed  (or 
lobed)  feet  and  are  expert  in  swimming  and  diving.  The 
wings  are  usually  small  or  rudimentary.  In  many  the  tail 
is  rudimentary.  Our  local  examples  are  the  grebes  and 

loons,  though  these  are 
little  seen  except  by  the 
field  naturalist,  hunter,  or 
fisher.  Their  legs  are  set 
far  back  in  adaptation  to 
their  main  use,  the  result 
being  that  they  must  stand 
upright  and  can  hardly 
walk.  The  plumage  is 
thick  and  well  oiled,  to 
fit  them  for  diving.  Water 
does  not  penetrate  be- 
tween the  feathers,  so  the 
skin  is  not  wet.  The 
grebes  have  lobed  toes 
and  are  about  the  size 

of  our  smallest  ducks.  They  dive  like  a  flash  when 
alarmed,  but  it  is  not  true  that  they  can  dive  between  the 
flash  of  a  gun  and  the  time  that  the  shot  can  reach  them. 
The  grebe  is  commonly  called  "  hell-diver."  The  loon  is 
our  largest  diver.  Its  peculiar  cry,  sometimes  resembling 
a  hysterical  laugh,  has  given  rise  to  the  expression,  "  crazy 
as  a  loon."  The  loon  does  not  try  to  escape  pursuers  by 
flight,  but  dives  and  swims  long  distances  under  water,  so 
that  it  is  seldom  shot. 


FIG.  131.    PIED-BILLED  GREBE  OR 
HELL-DIVER. 

From  Eckstorm's  The  Bird  Book, 


Aves. 


225 


The  auks  and  puffins  are  found  in  vast  numbers  on 
the  coast  of  Labrador  and  northward,  some  having  great 
powers  of  flight. 


FIG.  132.    THE  LOON. 

From  Eckstorm's  The  Bird  Book. 

The  penguins  are  correspondingly  characteristic  of  Pata- 
gonia and  the  Antarctic  regions.  Their  wings  are  small 
and  paddlelike,  and  ^ 

are  covered  with  scale- 
like  feathers. 

The  Long-winged 
Swimmers.  — This 
group  includes  the 
gulls  and  terns.  They 
are  web-footed  and 
have  long  wings  and 
tail,  with  remarkable 
power  of  flight.  They 
occasionally  rest  upon 
the  water,  coming  on 

shore  only  to  lay  their  eggs.     They  are  mostly  sea  birds, 
though  some  frequent  inland  lakes  and  rivers,  and  any  one 


FIG.  133.    HERRING  GULL. 

From  Eckstorm's   The  Bird  Book. 


226 


Descriptive  Zoology. 


who  has*  taken  a  trip  by  steamer  has  watched  them  and 
wondered  at  their  tireless  flight.  The  gulls  have  hooked 
beaks,  while  those  of  terns  are  pointed  and  nearly  straight ; 
in  both  the  bills  are  often  bright-colored.  They  feed  chiefly 
on  fishes,  but  some  are  scavengers,  following  ships. 

The  Tube-nosed  Swimmers.  —  To  this  order  belong  the 
petrels,  which  resemble  the  gulls  except  in  having  the  nos- 


FIG.  134.    PETREL. 

From  Eckstorm's  The  Bird  Book. 

trils  open  as  two  parallel  tubes  on  the  top  of  the  beak. 
Perhaps  best  known,  or  at  least  most  read  about,  are  the 
stormy  petrels,  or  "  Mother  Carey's  chickens."  Closely 
related  also  is  the  albatross  of  the  southern  hemisphere, 
which  has  a  spread  of  ten  feet. 


Aves.  227 

The  Totipalmate  Birds.  —  As  the  name  indicates,  the 
birds  of  this  order  have  full-webbed  feet ;  that  is,  there 
are  not  merely  two  webs  between  the  three  front  toes,  as 
in  ducks  and  most  web-footed  birds,  but  there  are  three 
full  webs,  the  hind  toe  being  connected  by  a  web  with  the 


FIG.  135.    THE  CORMORANT. 

From  Eckstorm's  The  Bird  Book. 

inner  front  toe.  Our  most  familiar  examples  are  the  cor- 
morants, but  they  are  shy  birds,  found  in  the  lakes  and 
larger  streams.  They  are  voracious  fish  eaters.  Nearly 
every  one  has  seen  the  pelican,  as  it  is  frequent  in  zoologi- 
cal gardens  and  menageries.  The  cormorant  has  a  rudi- 
ment of  the  throat  pouch  so  conspicuous  in  the  pelican 


228 


Descriptive  Zoology. 


In  the  East  Indies  the  pelican  is  tamed  and  used  in  fish- 
ing, as  is  the  cormorant  in  China. 

The  Ducks  and  Geese.  — These  birds  have  webbed  feet, 
with  heavy,  oily  plumage.  The  body  is  flattened,  and  all 
are  fine  swimmers.  The  bill  is  frequently  broad,  with  a 
sort  of  saw  edge.  The  tongue  is  fleshy.  In  the  geese  and 
fish  ducks  the  bill  is  narrow.  The  swans  belong  to  this 


FIG.  136.    HEAD  OF  PELICAN. 

From   Eckstorm's    The  Bird  Book. 

group.  Our  domesticated  duck  closely  resembles  the  wild 
mallard,  from  which  it  is  descended.  The  downy  feathers 
are  much  used  for  pillows,  etc.  Some  ducks  dive  well, 
and  live  largely  on  fish,  which  diet  gives  their  flesh  a  rank, 
fishy  flavor ;  but  the  fine  flavor  of  the  canvasback  is 
thought  to  be  due  to  the  wild  celery  on  which  it  feeds. 
The  wood  duck,  and  a  few  others,  are  exceptional  in 
nesting  in  trees,  though,  of  course,  near  water.  Ducks  and 


Avcs. 


229 


geese  attract  attention  by  their  migration  in  large  flocks, 
especially  in  the  spring.  But  their  former  vast  numbers  have 
been  reduced,  mainly  by  those  who  shoot  them  for  market. 

All  the  above-described  orders  are  often  classed  together 
as  the  "  swimming  birds." 

Herons  and  Storks.  —  These  are  slender-bodied,  long- 
legged,  and  long-necked,  with  long,  sharp  bills,  living 
about  the  water  and  feeding  chiefly  on  fishes,  etc.  They 
are  fitted  for  wading,  not  only  by  their  long  legs,  but  also 


FIG.  137.    WOOD  DUCK. 

From  Kingsley's  Zoology. 

by  the  fact  that  the  feathers  extend  only  part  way  down 
the  tibia.  The  long  neck  is  ordinarily  kept  bent  in  an 
S-shape,  and  can  be  quickly  darted  out  to  seize  food. 
Among  the  herons  are  the  big  blue  heron,  seen  along 
the  rivers  and  creeks,  the  white  egret,  the  bittern  or  stake 
driver,  the  night  heron,  and  the  little  green  heron.  In  the 
breeding  season  the  head  bears  long  plumes  that  are  much 
sought  as  ornaments. 


230  Descriptive  Zoology. 

The  Cranes  and  Rails. — This  group  also  consists  of  marsh 
birds,  usually  with  long  legs  and  necks.  The  cranes  are 
large,  the  white  or  whooping  crane  having  a  very  long 
windpipe  coiled  in  a  hollow  in  the  breastbone.  The  rails 
are  smaller  birds,  not  larger  than  a  hen.  These  are  seldom 
seen  except  in  reedy  swamps.  The  coot,  or  mud  hen,  is 
common  in  marshes  and  reedy  lakes  ;  it  has  a  bill  like  a  hen. 
It  is  an  excellent  swimmer,  but  has  lobed  instead  of  webbed 
feet.  The  flesh  is  rather  rank ;  but  as  ducks  are  becoming 
more  scarce,  the  coot  is  not  unfrequently  substituted. 

The  Shore  Birds.  — This  order  includes  the  snipes,  plovers, 
etc.  Like  the  two  preceding  orders,  its  members  usually 
have  long  bills,  neck,  and  legs.  The  three  orders  are  often 
spoken  of  together  as  the  "  waders."  The  long,  slender  bill 
is  often  soft  and  sensitive  at  the  tip,  to  fit  it  for  probing  in  the 
mud  for  worms.  Several  of  the  snipes  are  highly  esteemed 
by  epicures,  especially  the  woodcock  and  "jacksnipe." 

The  plovers  are  found  rather  more  on  dry  land ;  they 
have  no  hind  toe.  The  golden  plover  is  often  seen  in  large 
flocks  during  its  migration,  and  nearly  every  one  knows  the 
killdeer  by  the  cry  from  which  it  gets  its  name. 

The  Gallinaceous  Birds.  —  The  Gallinae,  or  fowls,  have 
robust  bodies,  well-developed  legs,  strong,  blunt  bills  and 
claws.  The  hind  toe  is  elevated,  that  is,  is  attached  higher 
than  the  other  toes.  They  are  poor  fliers,  having  relatively 
short  wings.  They  are  essentially  ground  birds,  none 
making  their  nests  in  trees.  They  feed  chiefly  on  seeds 
and  grains,  the  crop  and  gizzard  being  well  developed. 
On  account  of  their  plump  bodies  and  the  excellent  quality 
of  their  flesh,  they  are  valued  as  food.  Other  animals  thari 
man  prey  upon  them  ;  and  as  they  live  on  the  ground, 
where  prowling  enemies  can  gain  easy  access  to  them,  we 
should  expect  to  find  them  colored  for  protection ;  and,  in 


Aves.  23 1 

fact,  they  wear  grays,  browns,  and  blended  colors  resembling 
grass,  weeds,  and  brush.  The  turkey  is  a  native  American, 
though  bearing  a  foreign  name.  Except  the  turkey,  all  our 
native  Gallinae  belong  to  the  grouse  family. 

The  quail  is  widely  known  as  "bob-white."  It  is  very 
cunning,  and  holds  its  own  fairly  well  when  properly  pro- 
tected by  law. 

The  partridge,  or  ruffed  grouse,  lives  in  the  woods.  On 
account  of  its  wildness,  it  persists  where  native  forest  still 
stands.  It  makes  a  loud  noise  by  beating  its  wings  rapidly 
(drumming). 

The  prairie  hens  once  abounded  on  the  prairies  of 
the  Central  states,  but  are  fast  disappearing.  Even  though 
protected  by  law  eleven  months  of  the  year,  they  seem 
doomed  to  extermination.  They  lack  the  cunning  of  the 
quail,  and  their  size  is  a  disadvantage.  The  cock  has  a 
bare  colored  spot  on  each  side  of  the  neck.  This  is  inflated 
while  making  his  booming  noise  in  the  mating  season,  and 
gives  him  the  appearance  of  having  an  orange  on  each  side 
of  the  neck. 

The  sage  grouse  (sage  hen)  is  found  on  the  Western 
plains  among  the  sage  brush.  Sage  hens  are  very  good  to 
eat  early  in  the  season,  but  later  are  often  tainted  by  eating 
sage  leaves,  which  makes  the  flesh  bitter.  The  sage  hen 
is  peculiar  in  lacking  a  gizzard. 

One  of  the  most  interesting  of  the  grouse  is  the  ptarmi- 
gan. It  is  a  rock  grouse.  The  American  species  is  found 
in  the  Rocky  Mountains,  living  on  the  rocks  above  timber 
line.  The  legs  and  feet  are  fully  feathered  down  to  the 
base  of  the  claws.  It  has  in  summer  a  mixed  gray  and 
brown  color  that  makes  it  inconspicuous  on  lichen-covered 
rocks.  In  the  winter  it  turns  pure  white,  and  in  fall  and 
spring  is  partly  gray  and  partly  white  in  transition. 


2J2 


Descriptive  Zoology. 


Our  common  fowl  are  descendants  of  the  jungle  fowl  of 
India,  which  our  ancestors  took  from  a  wild  state  and  do- 
mesticated. The  guinea  fowl,  peafowl,  and  turkey  are 
other  domesticated  gallinaceous  birds,  these  domesticated 
forms  all  belonging  to  the  pheasant  family.  It  is  remark- 


FIG.  138.    THE  RUFFED  GROUSE. 

From  Eckstorm's  The  Bird  Book, 

able  that  the  breast  muscles  should  retain  their  large  size 
when  they  are  so  little  used.  Of  late,  pheasants  from  the 
old  world  have  been  introduced  in  various  parts  of  this 
country.  The  Gallinae  are  undoubtedly  the  most  valuable 
to  man  of  any  order  of  birds. 


Aves.  233 

The  Doves. — The  doves- are  characterized  by  a  soft, 
swollen  membrane,  or  cere,  overhanging  the  nostrils  at  the 
base  of  the  bill.  They  are  strong  fliers,  with  heavy  flying 
muscles  and  small,  weak  legs.  This  is  a  small  order.  The 
wild  pigeon,  formerly  existing  in  countless  numbers,  is  now 
well-nigh  extinct.  The  turtledove,  or  mourning  dove,  how- 
ever, remains  abundant  in  the  Central  and  Western  states, 
finding  abundant  feed  in  the  grain  fields. 

The  Birds  of  Prey.  —  Birds  of  prey  usually  have  stout, 
hooked  beaks  and  sharp,  curved  claws,  fitting  them  for 
clutching  and  tearing  their  prey.  They  do  not  have  a 
gizzard,  not  needing  such  a  stomach  for  digesting  flesh. 
The  colors  are  usually  dull,  the  sexes  generally  being 
colored  alike.  The  females  are  usually  larger  than  the 
males.  There  are  three  principal  forms  of  Raptorcs,  illus- 
trated by  the  hawk,  the  owl,  and  the  vulture. 

The  hawks  are  the  best  examples  of  the  order.  They  are 
keen-eyed,  strong  of  wing  and  leg.  There  is  much  un- 
grounded prejudice  against  them,  for,  with  the  exception 
of  Cooper's  hawk  and  the  sharp-shinned  hawk,  most  of 
them  do  more  good  than  harm,  killing  large  numbers  of 
mice,  especially  field  mice.  The  eagles  belong  to  the  same 
family  (Falconidae)  as  the  hawks.  The  so-called  "  bald- 
headed  eagle  "  is  not  bald ;  but  in  old  age  the  feathers  of 
the  head  and  neck  are  white,  making  the  name  "white- 
headed  eagle  "  appropriate.  The  adult  is  smaller  than  the 
younger  eagle.  This  bird  hardly  deserves  to  be  chosen  as 
the  emblem  of  this  country,  as  he  is  a  notorious  robber. 
Often  he  perches,  waiting  and  watching,  till  an  osprey,  or 
fishhawk,  has  captured  a  fish ;  then  he  swoops  down  upon 
him  and  snatches  away  the  prize.  The  golden  eagle  is  a 
distinct  species,  characterized  by  being  full-feathered  down 
to  the  toes. 


234 


Descriptive  Zoology. 


The  owls  have  both  eyes  facing  forward.  The  eyes  are 
large,  and  have  very  dilatable  pupils,  thus  enabling  them  to 
see  well  at  night.  Owls  have  a  soft  plumage  and  an  almost 
noiseless  flight.  They  depend  more  on  stealth  than  on 
swiftness  for  securing  their  prey.  They  do  much  good  by 


FIG.  139.    THE  MARSH  HAWK. 

From  Grinnell's  Our  Feathered  Friends. 

destroying  rats  and  mice.  They  swallow  birds  and  mice 
nearly  whole  ;  later  the  bones,  hair,  and  any  other  indigesti- 
ble portions  are  ejected  from  the  mouth.  Many  owls  have 
tufts  of  feathers  called  "ears,"  "ear  tufts,"  or  "horns," 
but  these  probably  are  merely  ornamental.  The  great 
horned  owl  is  well  known  by  its  hoot,  "  hoo-hoo,  hoo-hoo, 


Aves. 


235 


hoo-hoo,  hoo-hoo,"  the  last  note  prolonged  with  a  circum- 
flex accent. 

The  common  little  screech  owl  shows  an  interesting  varia- 
tion in  color.  Two  colors  are  found,  a  gray  and  a  reddish. 
It  was  at  first  thought  they  belonged  to  different  species, 
but  these  two  colors  have  been  found  in  young  of  the  same 
brood.  The  difference  seems  to  have  no  relation  to  age, 


FIG.  140.    TURKEY  BUZZARD. 

From  Grinncll's  Our'  Feathered  Friends. 

sex,  or  geographical  distribution,  nor  do  there  seem  to  be 
intermediate  individuals.  There  are  evidently  two  styles 
of  dress  with  the  screech  owls.  This  occurrence  of  two 
styles  of  plumage  is  known  as  "color  dimorphism." 

The  vultures  are  degenerate  Raptores,  usually  carrion 
eaters.  The  head  and  neck  are  usually  bare,  and  the  bill 
and  claws  weaker  than  in  the  above-described  forms.  Many 


23  6  Descriptive  Zoology. 

of  them  are  large,  and  soar  gracefully  hour  after  hour  high 
in  the  sky  ;  but  when  they  descend  to  earth  they  show  their 
disgusting  nature.  Yet  they  are  useful  as  scavengers,  and 
are  wisely  protected  by  law,  especially  in  the  South.  Our 
only  example  in  the  Northern  states  is  the  turkey  buzzard, 
which  has  a  spread  of  six  feet.  In  the  South  is  found  also 
the  carrion  crow.  This  must  not  be  confused  with  our 
common  crow,  which,  though  carnivorous,  is  classed  with 


FIG.  141.    CAROLINA  PARRAKEET. 

From  Kingsley's  Zoology. 

the  Passeres,  or  perching  birds.  The  condor  of  the  Andes 
is  a  vulture ;  though  feeding  chiefly  on  carrion,  it  sometimes 
kills  lambs  and  other  small  animals.  Exaggerated  accounts 
of  its  size  and  ferocity  are  common ;  measurements  do  not 
show  that  it  exceeds  a  spread  of  eleven  or  twelve  feet. 

The  Parrots.  —  Parrots  have  a  soft,  fleshy,  mobile  tongue, 
and  can  learn  to  talk.  They  have  the  toes  in  pairs,  and 
can  climb  well.  The  bill  is  large  and  so  strong  they  can 


Aves. 


237 


crack  hard  nuts.  Most  of  the  group  are  tropical  birds,  as 
the  macaws  and  cockatoos,  and  have  gorgeous  colors. 
The  only  example  of  the  order  found  in  the  United  States 
is  the  parrakeet  of  Florida. 

The  Cuckoos.  —  The  cuckoos  have  the  toes  in  pairs,  the 
outer   front  toe  having   been  turned   backward.     In  the 
same   group    are   placed 
the    kingfishers,    though 
this  order  is  confessedly  a 
"  mixed    lot  "   that   were 
thrown    out    of   the   old 
group     of     "climbing 
birds." 

The  Woodpeckers. — 
The  woodpeckers  are 
typical  climbers,  the  feet 
being  zygodactyl,  that  is, 
with  two  toes  turned 
forward  and  two  back- 
ward. In  climbing,  the 
stiff  tail  feathers  assist  by 
bracing  against  the  tree 
below.  The  bill  is 
straight,  hard,  and  chisel- 
like,  the  strong  neck 
muscles  using  it  to  drill 
a  hole  through  bark  and 
wood  after  insect  larvae. 
When  the  larva  is  reached, 
it  is  secured  by  the  slender  tongue,  hard  and  barbed  at  the 
tip,  which  is  darted  out  and  withdrawn  with  force  and  pre- 
cision. The  mechanism  for  projecting  the  tongue  can 
hardly  be  understood  without  actual  examination.  There 


FIG.  142.    DOWNY  WOODPKCKER. 

From  Grinnell's  Our  Feathered  Friends. 


23  8 


Descriptive  Zoology. 


are  two  slender  cartilaginous  rods  which  pass  backward 
from  the  tongue  under  the  angle  of  each  jaw,  up  and  for- 
ward on  top  of  the  head,  in  some  cases  even  nearly  to  the 
tip  of  the  bill.  The  cartilaginous  rods  furnish  stiffness,  so 
that  a  muscular  sheath  can  be  effective.  Woodpeckers  do 
good  by  destroying  borers.  Only  one  kind,  the  true  sap 

sucker,  or  yellow-bellied  wood- 
pecker, uses  the  wood  or  sap,  thus 
being  somewhat  injurious. 

The  Swifts  and  Humming 
Birds.  —  The  birds  of  this  order 
have  long,  pointed  wings,  the 
primaries  being  especially  elon- 
gated. The  feet  are  small  and 
weak.  The  swifts  are  well  known 
to  every  one  under  the  name 
"  chimney  swallows,"  but  they 
are  not  closely  related  to  the  true 
swallows.  The  humming  birds 
are  the  smallest  of  birds  and 
among  the  most  beautifully 
colored.  The  tongue  is  long 
and  extensible,  and  is  used  in 
securing  insects  from  tubular  flowers,  over  which  they 
are  often  seen  hovering. 

The  nighthawk  and  whip-poor-will  are  in  this  order. 
They  are  fitted  for  catching  insects  on  the  wing  by  the 
very  wide  mouth,  the  gape  extended  far  along  each  cheek, 
while  the  bill  itself  is  small  and  weak.  These  birds  fly  at 
night  or  at  dusk.  When  they  light  on  a  branch,  they 
always  sit  lengthwise,  never  crosswise,  and,  as  they  lie 
quite  flat  and  are  of  a  grayish  tint,  they  are  very  hard  to 
see. 


FIG.  143.    NIGHTHAWK. 

From  Packard's  Zoology. 


Aves. 


The  Perching  Birds.  —  This  is  the  largest  order  of  birds. 
Its  members  have  the  toes  fitted  for  perching,  with  three 
toes  turned  forward  and  one  backward,  all  on  the  same 
level;  most  of  them  are  "tree"  birds,  and  are  small  or 
medium-sized.  There  are  usually  twelve  tail  feathers  and 
nine  or  ten  primaries. 

The  flycatchers  include  the  kingbird  and  pewee.  The 
crows  and  jays  are  known  by  their  harsh  voices,  omnivo- 
rous appetites,  and  thievish  habits.  They  do  harm  by 
eating  the  eggs  and  young  of  many  birds.  The  black- 
birds and  orioles  form  a  well-known  family,  including 
the  parasitic  cowbird,  the  bobolink,  and  meadow  lark. 
The  sparrows,  or  finches,  are  the  largest  family  of  perchers. 
They  have  stout,  cone-shaped  beaks,  with  the  "  corners  of 
the  mouth  drawn  down." 
Most  of  the  sparrows  are  of 
rather  dull  colors,  streaked 
grays,  drabs,  and  browns  pre- 
vailing, as  in  the  tree  sparrow, 
chipping  sparrow,  and  snow- 
bird. Still,  many  of  these 
have  patches  of  yellow,  white, 
or  chestnut  feathers.  Some 
are  conspicuously,  colored,  as 
the  purple  finch,  wild  canary, 
or  thistle  bird,  the  indigo  bird, 
and  the  cardinal  and  rose- 
breasted  grosbeaks. 

The  English  sparrow  was  introduced  into  the  United 
States  about  1850,  with  the  hope  that  it  might  check  the 
ravages  of  the  "cankerworm"  and  other  tree-infesting 
caterpillars.  The  importation  was  a  failure.  It  is  doubt- 
ful if  these  sparrows  do  much  good  in  the  way  of  eating 


FIG.  144.    KINGBIRD. 

From  Packard's  Zoology, 


240  Descriptive  Zoology. 

obnoxious  insects.  Certain  it  is  that  the  English  sparrow 
drives  away  many  birds  that  were  very  useful  in  destroy- 
ing such  insects.  The  English  sparrow  is  a  bold,  pugna- 
cious bird ;  he  makes  himself  at  home,  but  drives  from 
home  many  of  our  fine  birds,  such  as  the  bluebird,  pewee, 
and  wren.  This  sparrow,  like  most  sparrows,  is  mainly  a 
seed  eater,  and  does  considerable  damage  in  this  way.  A 
further  charge  against  him  is  his  dirty  habits. 

The  swallows  are  another  interesting  family,  comprising 
the  "  swallow-tailed  "  barn  swallow,  the  eave  swallow,  the 


FIG.  145.    BUTCHER  BIRD  ;  SHRIKE. 

From  Miller's  My  Saturday  Bird  Class. 

bank   swallow,  which   makes  its  nest  in  long,  horizontal 
holes  in  steep  banks,  and  the  half-domesticated  martin. 

The  shrikes  are  hawklike  in  appearance  and  in  habits, 
having  a  hooked  beak  and  sharp  claws.  They  catch  mice, 
frogs,  small  birds,  snakes,  grasshoppers,  etc.,  and  impale 
them  on  the  thorns  of  hedges  and  other  trees.  From  these 
habits  they  are  also  called  mouse  hawks  and  butcher  birds. 
A  large  family  of  small  birds  called  warblers  live  in  tree 
tops,  and  are  not  well  known  except  to  those  who  take 
special  pains  to  study  them.  The  sprightly  wrens  are 
placed  in  the  same  family  with  the  mocking  bird,  catbird, 
and  brown  thrush.  These  last  three  are  superb  singers. 
Another  fine  songster  is  the  wood  thrush  ;  though  placed  in 


Aves. 


241 


a  different  family,  it  resembles  the  brown  thrush  in  hav- 
ing a  tawny  back  and  a  light-colored  breast,  with  brown 
spots,  the  tail  being  shorter  than  that  of  the  brown  thrush. 
The  mocking  bird  is  more  southern,  occurring  mainly 
south  of  the  latitude  of  the  mouth  of  the  Ohio  River.  The 
nuthatch  and  chickadee  remain  through  the  winter,  as  they 
feed  on  insects  found  beneath  the  bark  of  trees.  The  nut- 
hatch has  the  climbing  habits  of  a  woodpecker,  but  its 


FIG.  146.    BLUE  JAY. 

From  GrinnelFs  Our  Feathered  Friends. 

toes  are  arranged  as  in  perchers.  It  is  not  excelled  as  a 
climber,  going  sideways  or  head  downward,  as  well  as  up- 
ward. Among  the  highest  in  development  of  all  birds  is 
the  bluebird,  which,  unfortunately,  is  growing  rare  in  the 
Central  states,  especially  about  towns,  where  it  was  formerly 
common.  Perhaps  no  bird  ranks  higher  in  its  general 
organization  than  that  bird  so  dear  to  every  American 
child,  the  robin. 


242 


Descriptive  Zoology. 


Fossil  Birds.  —  In  rocks  in  various  parts  of  the  world 
have  been  found  remains  of  various  extinct  birds.  Some 
of  them  were  larger  than  any  existing,  —  ten  feet  in  height. 
One  egg  has  been  found,  the  capacity  of  which  equaled  one 
hundred  and  fifty  hen's  eggs.  But  more  interesting  than 
the  great  size  is  the  peculiar  structure  of  some  of  these 
ancient  birds.  Many  of  them  possessed  teeth,  and  some 


FIG.  147.    MEADOW  LARK. 

From  Grinnell's  Our  Feathered  Friends. 

of  these  teeth  were  set  in  sockets,  a  feature  we  did  not 
find  till  we  reached  the  highest  of  the  reptiles.  One  fossil, 
found  in  Bavaria,  had  not  only  teeth,  but  also  a  long  tail, 
consisting  of  many  vertebrae,  with  a  pair  of  feathers 
extending  out  on  each  side  from  each  joint. 

Relations  of  Birds  and   Reptiles.  —  Not  only  do  fossil 
remains  show  points  of  structure  in  common  between  these 


Aves. 


243 


two  groups,  but  if  we  compare  the  structure  of  modern  birds 
and  reptiles,  we  find  likenesses  that  are  not  apparent  on 
superficial  examination.  Feathers  and  scales  are  of  the 
same  origin  ;  the  bird  has  both.  The  feathers  of  the  wing 
of  the  penguin  are  scalelike.  The  head  joins  the  first  ver- 
tebra in  the  same  way  in  both  by  a  single  occipital  condyle, 


FIG.  148.    BALTIMORE  ORIOLE  AND  NEST. 

From  Grinnell's  Our  Feathered  Friends. 

that  is,  the  head  pivots  on  a  single  rounded  process,  instead 
of  on  two,  as  in  our  bodies.  The  tongue  of  a  snake  is 
supported  in  the  same  way  as  in  a  bird,  and  both  are  more 
or  less  protrusible.  Both  lay  large  eggs,  and  there  are 
points  of  development  in  common  that  cannot  be  con- 
sidered here.  All  these  facts,  here  scarcely  hinted  at,  go 
to  show  that  birds  have  descended  (or  ascended)  from 


244  Descriptive  Zoology. 

reptiles.  Hence  many  authors  include  birds  and  reptiles 
in  the  one  group,  Sauropsida,  just  as  the  fishes  and  am- 
phibians are  placed  together  in  the  group  Ictyhyopsida. 

Game  Birds'.  —  The  principal  game  birds  are  the  various 
kinds  of  grouse  (the  quail,  prairie  hen,  partridge,  sage  hen), 
the  ducks  and  geese,  and  various  wading  birds,  including 
snipe,  rails,  plovers,  etc.  But  the  food  value  of  these  is 
not  great.  All  sportsmen  who  wish  a  continuation  of  these 
game  birds  should  agree  in  enacting  such  laws  as  shall 
protect  them  so  their  numbers  may  not  be  greatly  reduced. 
The  general  sentiment  is  that  they  ought  not  to  be  killed 
for  market  purposes,  nor  during  the  jreeding  season. 

Value  of  Birds.  —  The  value  and  importance  of  game 
birds  sinks  into  insignificance  in  comparison  with  the 
smaller  birds.  When  we  stop  to  consider  the  ravages  of 
insects,  those  that  infest  the  fields  and  orchards,  forests 
and  groves,  the  many  larvae  at  the  roots  and  on  the  foli- 
age, the  caterpillars,  cankerworms,  etc.  ;  and  on  the  other 
hand  the  multitude  of  birds  — mostly  of  small  size  —  the 
robin  and  bluebird,  the  cuckoos  and  warblers,  flitting  about 
in  the  tree  tops  all  day  long  in  search  of  these  noxious 
insects,  —  when  all  these  facts  are  weighed,  we  may  well 
raise  the  question  whether,  if  all  bird  life  on  the  globe 
were  destroyed,  the  earth  would  long  continue  habitable  by 
man.  As  it  is,  occasional  plagues  of  insects  strip  large 
areas  of  plants  and  bring  on  local  famine.  These  birds 
should  be  fully  protected  by  law.  Till  lately  the  number 
of  many  of  these  birds  has  rapidly 'decreased,  owing  to  their 
being  killed  for  their  plumage,  to  the  collection  of  eggs, 
and  to  wanton  and  aimless  destruction.  Besides  game  birds 
none  should  be  killed,  except  for  scientific  purposes,  unless 
they  are  themselves  noxious,  as  crows  and  jays,  the  English 
sparrow,  a  few  hawks,  and  possibly  a  few  others. 


Aves. 


245 


General  Characteristics  of  Birds. — The  possession  of 
feathers  is  sufficient  to  distinguish  birds  from  all  other 
animals.  The  consolidation  of  the  thoracic  ,vertebrae  and 
the  pelvis  is  peculiar.  The  bones  of  the  cranium  are 
united  in  one,  the  sutures  disappearing  early.  The  ribs 
are  provided  with  flat  braces  extending  to  adjoining  ribs. 
The  breastbone  is  large,  and  usually  has  a  well-developed 
keel.  The  two  collar  bones  (clavicles)  unite  to  form  a  wish- 
bone. Air  sacs  are  connected  with  the  lungs.  The  tem- 
perature of  the  blood  is  high.  The  red  corpuscles  are 
elliptical  and  have  nuclei.  The  brain  is  relatively  large, 
the  eye  especially  being  large  in  proportion  to  the  size 
of  the  head.  The  organ  of  the  voice  is  at  the  lower  end  of 
the  windpipe,  instead  of  at  the  upper. 


Class  Aves 


CLASSIFICATION   OF  BIRDS. 

ORDERS.  EXAMPLES. 

Division  Ratitae  i.  Struthiones Ostrich 

2.  Pygopodes Loon 

3.  Longipennes .....  Gull 

4.  Turbinares Petrel 

5.  Steganopodes     ....  Pelican 

6.  Anserrs Duck 

7.  Herodiones Heron 

8.  Paludicolae     .     .          .     .  Crane 
Division  Carinatae    i     9.  Limicolae Snipe 

10.  Gallinae      .     .     .     .     .     .  Quail 

11.  Culumbas Pigeon 

12.  Raptores    ......  Hawk 

13.  Psittaci Parrot 

14.  Coccyges Cuckoo 

15.  Pici Woodpecker 

16.  Macrochires Nighthawk 

17.  Passeres Robin 


CHAPTER   XVI. 
BRANCH   CHORDATA. 

CLASS   MAMMALIA. 
Example. —  The  Common  Rabbit. 

Habits.  —  The  common  gray  rabbit  is  familiar  to  many 
under  the  name  of  "  cottontail."  This  name  is  due  to  the 
white  fur  of  the  ventral  surface  of  the  tail.  As  the  tail 
is  held  erect,  the  white  part  is  very  conspicuous  when  the 
rabbit  is  running  away  from  the  observer.  Our  rabbit 
—  unlike  the  English  rabbit  —  does  not  burrow,  though  it 
sometimes  takes  to  holes  to  escape  pursuit,  and  perhaps 
lives  in  them  when  other  shelter  is  not  convenient.  In 
pleasant  weather  the  rabbits  stay  most  of  the  time  in 
rather  open  spaces,  hiding  in  bunches  of  grass.  They  do 
not  make  any  nest  at  such  places,  but  simply  find,  or  make, 
an  opening  in  a  convenient  tuft  of  grass,  where  they  squat. 
Such  place  is  called  a  "  form."  In  colder  weather,  especially 
when  there  is  snow,  they  find  a  more  complete  protection 
in  brush  heaps,  hedges,  and  patches  of  weeds,  or  even  in 
burrows.  They  are  nocturnal,  sitting  quiet  all  day,  or 
coming  out  only  in  the  cool  part  of  the  summer  mornings 
and  evenings.  But  at  night  they  come  out  and  run  about 
for  food,  and  many  observers  think  they  are  very  social  and 
enjoy  playing  together. 

Covering  of  the  Rabbit.  —  The  rabbit  has  a  covering  of 
hair.  The  bulk  of  the  covering,  the  fur,  is  made  up  of 
short,  soft  hairs.  Among  these,  and  more  deeply  embedded 

246 


Mammalia.  247 

in  the  skin,  are  a  number  of  long,  straight  hairs  with  dark 
tips.  They  make  an  admirable  covering  during  the  cold  of 
winter.  The  feet  are  also  covered  by  hairs,  and  the  inside 
of  the  cheek  is  hair-lined. 

The  Rabbit's  Mode  of  Locomotion.  —  It  should  first  be 
observed  that  the  hind  limbs  are  much  larger  and  stronger 
than  the  fore  limbs.  The  back  and  loins  are  well-muscled, 
all  fitting  the  rabbit  for  running.  When  it  is  undis- 
turbed, and  moving  about  in  search  of  food,  it  simply 
hops.  But  when  frightened,  it  runs  swiftly.  In  running, 
the  chief  propelling  power  is  the  hind  limbs,  which,  when 
straightened,  are  efficient  means  in  pushing  the  body  for- 
ward. Before  each  leap  the  body  is  doubled,  or  arched. 
Then  the  body  straightens  by  the  action  of  the  muscles  of 
the  back  and  the  hind  limbs.  At  the  end  of  the  long  leap 
the  rabbit  alights  on  the  front  feet,  but  the  long  hind  legs 
swing  forward,  one  on  each  side,  straddling  the  fore  legs, 
so  that  the  foremost  tracks,  in  the  set  of  tracks  made  at 
each  leap,  are  made  by  the  hind  feet,  and  the  two  smaller 
tracks,  which  are  closer  together,  are  made  by  the  front 
feet,  as  follows  :  — 

o  hind                                                        o 

front  o  o 

feet     o  o 

o  feet                                                       o 

Not  unfrequently  the  rabbit  sits  erect,  resting  on  the 
whole  length  of  the  hind  feet.  Ordinarily  the  rabbit  walks 
or  runs  on  the  toes  only.  The  true  heel  in  the  rabbit  is 
off  the  ground  in  running,  and  is  where  we  usually  cut  off 
the  foot  when  dressing  the  rabbit. 

Food  of  the  Rabbit. — The  rabbit  is  herbivorous,  eating 
clover,  grass,  etc.,  with  an  especial  liking  for  many  garden 
vegetables.  It  is,  therefore,  commonly  found  around  gar- 


248  Descriptive  Zoology. 

dens  and  orchards.  The  rabbit  likes  such  places,  not  only 
on  account  of  the  food  there  found,  but  also  because  of  the 
shelter  afforded  by  the  grass  and  bushes.  In  winter,  when 
fresh  vegetation  is  scarce,  the  rabbit  eats  twigs,  especially 
the  buds  and  bark ;  thus  a  brush  heap  of  fresh  cuttings 
from  such  trees  as  the  apple  affords  the  rabbit  both  shel- 
ter and  food. 

The  Rabbit's  Teeth.  —  At  the  front  of  the  mouth  are 
two  pairs  of  chisel-shaped  teeth,  the  incisors.  These  teeth 
are  mainly  composed  of  dentine.  On  their  front  surfaces  is 
a  layer  of  hard  enamel.  The  result  of  this  hard  front  edge 
is  that  in  gnawing,  the  hinder  edges  of  the  teeth  are  worn 
away  faster  and  the  teeth  are  kept  constantly  beveled  ;  in 
other  words,  they  are  self-sharpening.  These  teeth  grow 
at  the  base  of  the  roots  as  fast  as  they  are  worn  away  at 
the  outer  ends.  If  one  of  these  teeth  should  be  broken 
off,  or  otherwise  destroyed,  the  opposing  tooth  would  no 
longer  be  worn  down  and  would  grow  too  long,  and  sooner 
or  later  interfere  with  the  process  of  eating  and  cause 
starvation.  Many  cases  of  this  kind  among  rodents  have 
been  known.  Back  of  the  upper  incisors  is  another,  smaller 
pair  of  teeth,  also  regarded  as  incisors,  an  arrangement  pe- 
culiar to  the  rabbits  and  not  found  in  other  rodents.  Back 
of  the  incisors  is  a  considerable  space  without  any  teeth, 
before  the  grinding  teeth,  or  molars,  are  reached.  This 
space  undoubtedly  enables  the  rabbit  to  manage  the  mouth 
better  in  gnawing,  just  as  in  most  of  our  pinchers  we  have 
a  widened  space  back  of  the  nipping  jaws.  The  same 
arrangement  is  found  in  the  horse,  cow,  etc. 

The  molars  are  six  above  and  five  below,  set  in  close 
rows,  and  having  ridges  running  crosswise.  The  direction 
of  these  ridges  must  be  considered  in  relation  to  the  joint 
by  which  the  lower  jaw  articulates  witn  the  skull.  This 


250  Descriptive  Zoology. 

joint  is  not  a  regular  hinge  joint,  such  as  we  find  in  a  cat, 
which  allows  of  little  more  motion  than  a  door  hinge. 
The  rounded  knob  at  the  upper  end  of  each  jawbone  fits 
into  a  groove  which  runs  front-and-back,  thus  allowing  the 
jaw  to  be  moved  forward  and  back.  If  one  watches  a 
rabbit  chewing,  he  will  see  that  this  motion  is  character- 
istic in  place  of  the  more  decidedly  lateral  movement  seen 
when  a  cow  is  ruminating.  The  ridges  of  the  upper  and 
lower  molars,  therefore,  are  drawn  back  and  forth  over 
each  other,  thus  effectively  grinding  the  food. 

The  Process  of  Digestion.  —  There  are  four  pairs  of 
salivary  glands  on  each  side  of  the  head,  which  pour  their 
secretions  into  the  mouth  to  aid  in  digestion.  At  the  base 
of  the  tongue  is  the  epiglottis,  a  cartilaginous  cover  which 
turns  down  over  the  opening  into  the  windpipe  when  the 
food  passes  over  it  on  the  way  to  the  stomach.  The  gullet 
extends  through  the  thorax,  piercing  the  diaphragm,  and 
enters  the  large  stomach,  which  lies  back  of  the  diaphragm, 
partly  separated  from  it  by  the  liver.  On  the  liver  is  the 
bile  sac,  from  which  the  bile  is  poured  into  the  first  part 
of  the  intestine,  called  the  duodenum.  The  long,  coiled 
small  intestine  finally  joins  the  large  intestine,  and  at  their 
junction  is  a  long,  blind  tube,  or  sac,  the  cecum.  Near  the 
stomach  is  the  pale  pancreas,  which  empties  its  secretion 
by  a  duct  into  the  duodenum. 

Since  the  rabbit  eats  food  that  is  relatively  poor  in  nour- 
ishing material,  it  is  obliged  to  eat  a  large  amount ;  and  as 
vegetable  food,  especially  with  a  good  deal  of  cellulose,  is 
difficult  of  digestion,  we  should  expect  to  find  the  digestive 
tube  both  long  and  capacious,  and  this  is  the  case.  The 
intestine  is  about  ten  times  the  length  of  the  rabbit's  body. 
While  the  rabbit  sits  in  concealment  during  the  day,  the 
slow  process  of  digestion  is  going  on. 


Mammalia. 


251 


The  Circulation  of  Blood  in  the  Rabbit.  —  The  rabbit's 
circulation  is  essentially  as  in  our  bodies.  The  heart  is 
completely  divided  into  two  parts,  the  right  and  left  halves. 
The  right  half  pumps  the  blood  to  the  lungs,  whence  it 
returns  to  the  left  half  of  the  heart  to  be  pumped  to  all  the 
other  parts  of  the  body  through  the  main  artery,  called  the 
aorta.  The  heart  is  within  a  pericardium,  situated  between 
the  two  lungs,  and  resting  against  the  diaphragm,  near  the 
ventral  body  wall. 

How  the  Rabbit  Breathes.  —  The  rabbit's  respiration,  too, 
is  very  like  ours.  The  diaphragm  is  a  thin  sheet  of  muscle 
that  arches  across  the 
body  at  about  the  pos- 
terior border  of  the  longer 
ribs,  separating  the  body 
cavity  completely  into  two 
cavities,  the  anterior  con- 
taining the  heart  and 
lungs,  the  posterior  con- 
taining the  stomach  and 
intestines,  with  the  liver, 
pancreas,  kidneys,  blad- 
der, etc.  By  the  shorten- 
ing of  its  muscle  fibers  FlG'  I5°-  CROSS  SECTION  OF  ABDOMEN 

.  j  OF  MAMMAL. 

the  diaphragm  is  moved 

backward,  thus  drawing  in  the  air.  The  muscles  which 
move  the  ribs  in  and  out  also  do  part  of  the  work.  The 
lungs  are  similar  to  ours,  being  light  (hence  called 
"lights")  and  porous,  all  the  air  vesicles  being  reached 
by  minute  branches  of  the  bronchial  tubes,  which  fork 
from  the  windpipe.  The  temperature  of  the  rabbit's 
blood  is  considerably  higher  than  our  own,  averaging  103° 
or  104°  F. 


252  Descriptive  Zoology. 

The  Excretory  Organs  of  the  Rabbit.  —  The  lungs  act  as 
excretory  organs,  throwing  off  carbon  dioxid  as  well  as  ab- 
sorbing oxygen.  The  kidneys  also  are  organs  of  excretion. 
The  kidneys  are  bean-shaped  bodies  attached  to  the  dorsal 
wall  of  the  abdominal  cavity.  To  each  kidney  runs  a  branch 
of  the  aorta,  supplying  it  with  blood,  and  from  the  kidney  a 
vein  returns  the  blood  to  the  postcaval  vein.  As  the  blood 
flows  through  the  kidney  in  fine  tubes  called  capillaries,  the 
kidney  removes  from  it  certain  impurities,  especially  the 
waste  matter  that  contains  nitrogen.  The  excretion  is  con- 
veyed backward  by  a  tube  called  the  ureter,  and  emptied 
into  the  urinary  bladder,  an  organ  not  possessed  by  the 
birds  or  reptiles. 

Enemies  of  the  Rabbit  —  Among  the  enemies  of  the  rab- 
bit are  dogs,  wolves,  foxes,  cats,  both  wild  and  domesticated, 
minks,  weasels,  hawks,  owls,  and  perhaps  many  others.  In 
addition  to  these  larger  foes,  the  rabbit  is  usually  infested 
by  parasites,  such  as  fleas,  tapeworms,  etc. 

How  the  Rabbit  escapes  his  Enemies.  —  The  rabbit  has 
claws,  but  they  are  not  very  efficient  as  a  means  of  defense. 
Rabbits  use  their  teeth  in  fighting  one  another,  but  these 
avail  nothing  against  their  enemies.  The  rabbit  is  practi- 
cally defenseless,  and  relies  upon  two  means  for  protec- 
tion, —  the  first  is  its  color,  and  the  second  its  speed  of  flight. 
The  prevailing  color  of  the  rabbit  is  gray,  varied  with  some 
blackish,  and  more  or  less  tinged  with  yellowish  brown.  In 
the  summer  he  appears  rather  more  rusty  or  tawny.  He  is 
so  like  his  surroundings  that  it  takes  a  keen  and  practiced 
eye  to  detect  him  when  he  sits  perfectly  quiet  in  his  form. 
This  he  usually  does,  relying  on  his  color  to  protect  him. 
Besides  his  color,  his  position  is  an  aid  in  concealment,  for 
he  is  snugly  doubled  up,  the  ears  folded  down  closely  along 
the  back,  and  the  white  tail  is  out  of  sight.  He  generally 


Mammalia.  253 

sits  in  the  center  of  a  tuft  of  grass,  and  frequently  he 
appears  to  select  a  small  bunch  of  grass,  just  large  enough 
to  cover  him  scantily,  perhaps  thinking  that  he  will  not  be 
looked  for  in  such  slight  cover.  Sometimes  a  rabbit  will 
start  from  his  form  when  an  enemy  is  at  a  distance,  especially 
if  much  noise  is  made  ;  at  other  times  he  may  be  approached 
closely,  and  almost  touched,  before  he  will  stir.  When  he 
does  start,  it  is  usually  with  a  dash ;  and  he  generally  runs 
with  great  speed  to  another  cover,  often  running  through 
hedges  and  other  places  that  will  prove  an  obstruction  to 
pursuers.  If  followed,  especially  by  dogs,  the  rabbit  fre- 
quently runs  in  a  circle,  and  after  completing  the  circle, 
suddenly  jumps  far  to  one  side,  thus  throwing  the  follower 
off  the  scent.  Though  speedy,  the  rabbit  is  not  an  enduring 
runner.  He  carries  too  much  weight.  The  bulky  food  and 
the  large  amount  he  eats  prove  a  handicap.  His  paunch 
suggests  that  of  the  cow.  A  dog  has  the  advantage.  Being 
a  meat  eater,  he  has  a  short  intestine,  whereas  that  of  the 
rabbit  is  long.  The  dog's  food  is  concentrated,  nutritious, 
and  quickly  digested ;  hence  the  dog  is  light  in  the  abdo- 
men, where  the  rabbit  is  heavy.  Further,  the  heart  of  the 
dog  is  stronger  relatively,  and  a  strong  heart  is  the  chief 
factor  in  long-windedness.  But  in  spite  of  his  relative  short- 
windedness,  his  running  and  his  cunning  often  enable  him 
to  escape. 

Injury  done  by  the  Rabbit.  —  Rabbits  do  considerable 
harm  by  gnawing  the  bark  of  young  trees  in  orchards,  and 
in  some  places  it  is  necessary  to  build  a  protection  around 
the  trees  to  save  them.  The  English  rabbit,  introduced 
into  Australia,  has  become  a  plague.  In  spite  of  all  the 
means  that  man  has  been  able  to  devise,  they  multiply 
beyond  any  checks  that  can  be  applied.  High  rewards 
have  been  offered  for  any  means  that  will  exterminate 


254  Descriptive  Zoology. 

them,  and  bounties  are  continually  paid  for  killing  them ; 
they  thrive  in  spite  of  all  that  can  be  done.  The  intro- 
duction of  contagious  diseases  has  not  been  a  success. 

Uses  of  Rabbits.  —  In  this  country  they  are  used  only  for 
food,  and  that  to  a  very  slight  extent ;  but  in  Australia  and 
some  other  parts  of  the  world  the  fur  is  saved  and  used  in 
making  felt.  This  is  an  important  industry,  as  practically 
all  our  "  derby  "  hats  are  made  of  rabbit  fur.  Most  of  the 
fur  goes  to  London  to  be  dyed. 

Development  of  the  Rabbit.  —  The  ovaries  are  small  ovoid 
bodies  attached  to  the  dorsal  wall  of  the  abdominal  cavity, 
posterior  to  the  kidneys.  The  eggs  are  microscopic,  and 
when  set  free  from  the  ovary,  enter  the  free  opening  of  the 
oviducts,  as  in  the  case  of  the  frog.  The  posterior  end  of 
each  oviduct  is  developed  into  an  organ  called  the  uterus, 
for  holding  and  nourishing  the  egg,  which  is  here  retained 
till  development  to  the  form  of  the  parent  is  reached.  The 
young  are  born  alive,  and  for  a  time  after  birth  they  are 
nourished  by  milk  from  the  mammary  glands  of  the  mother. 
From  four  to  seven  are  usually  in  a  litter,  more  commonly 
five  or  six.  As  several  litters  may  be  produced  during  a 
year,  the  rate  of  their  increase  is  very  rapid ;  but  their  fa- 
talities are  enough  to  keep  their  numbers  down  in  this  part 
of  the  world.  The  little  "  cottontails  "  are  concealed  in  a 
fur-lined  nest,  which  is  a  pocketlike  hole  in  the  ground. 

The  Nervous  System  of  the  Rabbit.  —  The  brain  is  fairly 
well  developed, but  the  rabbit  has  not  a  high  intelligence;  and 
as  in  the  other  lower  orders,  the  surface  of  the  brain  is  nearly 
smooth  instead  of  convoluted,  as  is  the  case  with  brains  of 
the  higher  animals.  The  principal  parts  of  the  brain  are 
the  cerebrum,  with  its  two  hemispheres  tapering  forward 
into  the  olfactory  lobes  (see  Fig.  167).  Back  of  the  cere- 
brum is  the  irregular  cerebellum,  with  a  central  and  lateral 


Mammalia. 


255 


Jobes.  From  the  ventral  surface  of  the  brain  the  spinal 
bulb  arises,  and  continues  into  the  spinal  column  as  the 
spinal  cord.  From  the  brain  arise  twelve  pairs  of  cranial 
nerves,  and  from  the  spinal  cord  a  series  of  paired  spinal 
nerves  which  supply  the  body. 

The  Senses  of  the  Rabbit.  —  Sight  and  hearing  are  es- 
pecially well  developed.  The  eyes  are  prominently  placed 
on  the  sides  of  the  head,  so  that  the  rabbit  can  see  an  enemy 
approach  from  any  direction.  The  ears  are  long,  and  can 
be  moved  by  muscles  so  as  to  turn  in  any  direction  to  catch 
the  sound.  Rabbits  may  not  unfrequently  be  seen  to  sit 
erect  and  prick  up  the  ears  as  if  suspicious  of  danger. 
When  at  rest  in  concealment,  the  ears  are  laid  flat  on  the 
back.  The  sense  of  smell  seems  well  developed.  The  nos- 
trils are  longitudinal  slits  at  the  end  of  the  nose,  and  between 
them  is  a  cleft,  from  which  fact  we  borrow  the  term  "  hare- 
lip." This  arrangement  apparently  gives  greater  mobility 
to  the  lips  in  feeding,  and  in  sniffing  there  is  considerable 
range  of  movement  of  the  upper  lip  and  nostrils.  Taste 
also  appears  to  be  fairly  keen,  judging  by  the  rabbit's  dis- 
crimination in  choice  of  foods.  Microscopic  examination 
of  the  tongue  shows  essentially  the  same  taste  organs  and 
nerve  supply  as  in  our  tongues.  The  sense  of  touch  ap- 
pears to  be  distributed  all  over  the  body,  though  prob- 
ably more  keen  about  the  nose,  especially  through  the  long, 
stiff  hairs  which  we  commonly  call  the  "whiskers." 


CHAPTER   XVII. 
BRANCH   CHORDATA. 

CLASSIFICATION    OF   MAMMALIA. 
SUBCLASS  I.  —  PROTOTHERIA. 

THERE  are  two  subclasses  of  mammals,  the  Prototheria 
and  the  Theria.  The  Prototheria  nourish  the  young  with 
milk.  They  also  show  that  they  are  mammals  by  their 
hairy  covering.  But  they  reveal  their  relationship  to  birds 
and  reptiles  by  the  fact  that  they  lay  eggs. 


FIG.  151.    DUCKBILL. 

From  Packard's  Zoology,  after  Liitken. 

In  this  subclass  there  is  but  one  order,  the  Monotremata. 
The  order  contains  but  three  or  four  species,  and  there  are 
two  chief  forms,  the  duckbill  and  spiny  ant-eater,  both  lim- 
ited to  Australia  and  adjacent  islands. 

256 


Mammalia.  257 

The  duckbill  has  a  horny  bill  similar  to  that  of  a  duck. 
Its  habits  are  similar  to  those  of  a  muskrat.  It  lives  in 
water,  and  has  holes  in  the  bank,  which  it  can  enter  beneath 
the  water.  The  body  is  about  as  big  as  a  cat's,  though 
it  presents  a  "  squatty  "  appearance,  the  legs  being  very 
short.  The  feet  are  webbed  and  the  tail  is  flattened.  It  is 
covered  by  a  soft,  fine  fur.  The  duckbill  has  rudiments  of 
teeth  in  the  early  stages  of  its  life,  but  in  the  adult  state 
neither  the  duckbill  nor  the  spiny  ant-eater  has  any  teeth. 

The  ant-eater  is  of  about  the  same  size  as  the  duckbill. 
The  hairs  are  developed  into  strong,  stiff,  sharp  spines. 
The  bill  is  conical,  and  a  small  mouth  at  the  end  permits 
the  extension  of  the  slender  tongue,  with  which  it  licks  up 
ants  like  other  ant  eaters.  It  lives  in  rocky  ground. 

SUBCLASS  II.  — THERIA. 

The  Theria  include  all  the  remaining  mammals.  In  this 
subclass  the  young  are  born  alive,  in  the  form  of  the  adult. 

The  Marsupials.  —  Our  only  marsupial  is  the  opossum. 
This  odd  animal  is  well  known,  at  least  by  report,  on 
account  of  its  habit  of  feigning  death  when  attacked.  The 
marsupials  get  the  name  from  their  most  marked  charac- 
teristic, the  possession  of  a  pouch,  or  infolding  of  the  skin 
of  the  abdomen.  Two  peculiar  bones  extend  forward  from 
the  pelvis,  toward  the  pouch ;  they  are  called  the  mar- 
supial bones,  as  they  support  the  pouch.  The  young  are 
born  in  a  very  immature  condition,  and  are  transferred  to 
the  pouch,  where  they  are  nursed.  The  young  are  kept  a 
long  time  developing  in  the  pouch,  and,  after  they  become 
self-helpful,  occasionally  take  refuge  in  the  pouch.  The 
opossum  is  almost  omnivorous,  eating  insects,  eggs,  and 
birds,  the  teeth  being  of  the  carnivorous  type.  The  opossum 
is  a  good  climber,  and  has  a  hairless,  scaly,  prehensile  tail. 


258  Descriptive  Zoology. 

Opossums  are  very  tenacious  of  life,  and  it  is  commonly 
reported  that  after  a  "  possum  "  has  been  severely  pounded 
and  "  every  bone  in  its  body  broken,"  it  later  gets  up  and 
crawls  away.  The  following  are  some  facts  of  structure 


FIG.  152.    OPOSSUM. 

From  photograph  from  Recreation,  by  permission  of  G.  O.  Shields. 

that  may  explain  such  reports.  First,  the  skin  and  hair 
make  a  thick  protective  covering,  under  which  is  usually  a 
thick  layer  of  fat.  The  chewing  muscles  extend  far  up 
on  the  top  of  the  head,  meeting  in  the  middle  line.  The 


Mammalia.  259 

skull  is  therefore  well  protected,  so  that  it  may  receive  a 
severe  mauling  and  not  be  much  the  worse,  except  for 
external  bruises.  The  opossum  is  of  a  low  order  of  intelli- 
gence, and  appears  stupid,  both  when  free  and  in  confine- 
ment. It  has  not  sense  enough  to  become  a  pet. 

The  kangaroo  is  another  well-known  marsupial.  The 
story  of  its  development  is  about  the  same  as  that  of  the 
opossum,  but  the  mode  of  life  is  different.  The  hind  legs 
are  excessively  developed,  and  the  animal  hops  with 
"record-breaking"  power,  seldom  putting  the  feeble  fore 
legs  to  the  ground.  When  standing,  the  strong,  muscular 
tail  aids  in  supporting  the  body,  forming  a  third  leg,  so  to 
speak.  The  kangaroo  is  entirely  herbivorous.  There  are 
many  other  marsupials  in  Australia,  and,  in  fact,  with  the 
exception  of  the  opossums,  all  the  living  marsupials  are 
confined  to  ^he  Australian  region.  Many  countries  yield 
fossil  remains  of  marsupials,  some  of  large  size,  showing 
that  Australia  contains  the  remnants  of  this  peculiar,  but 
once  widely  distributed  race.  It  is  further  interesting  to 
note  that  Australia  has  no  other  native  mammals  than  the 
marsupials,  except  possibly  the  dingo,  or  wild  dog,  which 
some  believe  to  have  been  introduced. 

PLACENTAL   MAMMALS. 

All  the  mammals  above  the  marsupials  are  born  in  a 
more  mature  condition. 

The  Edentates.  —  This  order  includes  the  sloths,  arma- 
dillos, etc.  They  are"  not  wholly  toothless,  as  the  name 
would  indicate,  but  the  teeth,  when  present,  are  simple  or 
imperfect.  They  are  mostly  tropical,  one  armadillo  occur- 
ring in  southwestern  Texas. 

The  sloths  are  herbivorous  and  tree-inhabiting.  They 
climb,  hanging  under  limbs  by  their  hooked  claws,  and  as 


26o 


Descriptive  Zoology. 


they  proceed,  strip  off  the  leaves.  On  the  ground  they 
are  almost  helpless.  The  extinct  slothlike  megatherium 
was  as  large  as  a  rhinoceros. 

The  armadillos  have  a  scaly  or  horny  development  of 
the  skin  for  protection ;  some  have  also  the  power  of  roll- 
ing themselves  into  a  ball,  still  further  securing  safety. 

The  ant-eaters  lack  teeth ;  they  secure  insects  by  pro- 
truding the  long,  sticky  tongue. 

The  Gnawers.  —  The  gnawers,  or  rodents,  are  character- 
ized by  chisel-shaped  incisor  teeth,  which  keep  wearing 
away  at  the  tip  and  as  continually  growing  from  the  root. 


FIG.  153.    NINE-BANDED  ARMADILLO. 

From  Packard,  after  Liitken. 

In  all  but  the  hares  the  incisors  are  two  above  and  two 
below.  There  are  no  canine  teeth,  and  there  is  a  wide 
space  between  the  incisors  and  the  molars.  They  are 
chiefly  herbivorous,  and  the  digestive  tube  is  long.  They 
constitute  the  largest  family  of  mammals,  and  are  espe- 
cially numerous  in  individuals. 

The  Hares. — The  general  characteristics  of  this  family 
have  been  illustrated  in  the  description  of  the  rabbit. 
Besides  our  common  gray  rabbit,  there  are  found  in  the 
Southern  states  the  marsh  hare  and  the  water  hare ;  in  the 
North,  the  northern  hare,  which  turns  white  in  winter; 
on  the  Western  plains,  the  big  jack  rabbit. 


Mammalia.  261 

Porcupines.  —  The  porcupines  are  distinguished  by  hav- 
ing sharp  spines,  which  are  really  modified  hairs,  and  are 
scattered  among  the  longer  hairs  of  the  ordinary  type  so 
that  the  spines  are  ordinarily  not  very  conspicuous.  The 
spines  are  especially  developed  on  the  tail  and  on  the  pos- 
terior parts  of  the  body.  When  the  porcupine  is  attacked 
by  an  enemy,  and  especially  if  cornered,  he  turns  his  back 
toward  his  pursuer  and  draws  the  skin  of  the  body  forward, 
so  that  the  quills  point  outward  in  all  directions,  and  any 
attempt  to  seize  him  is  met  by  a  quick  side  stroke  of  the 
tail.  The  quills  have  a  very  sharp  tip,  near  which  are  a 
series  of  backward-projecting  barbs.  They  are  also  very 
loosely  attached  at  the  base.  The  result  is  that  the  quills 
readily  pierce  the  soft  skin  of  an  enemy,  become  detached 
from  the  porcupine,  and  remain  sticking  in  the  wound. 
These  facts  are  the  sole  foundation  of  the  once  widely  ac- 
cepted belief  that  the  porcupine  has  the  power  to  shoot 
his  quills  into  his  pursuer.  In  the  West  cattle  often  come 
in  contact  with  porcupines  and  have  their  legs  and  noses 
stuck  full  of  quills.  On  account  of  the  backward-project- 
ing barbs  the  quills  cannot  fall  out,  but  keep  working  their 
way  in  deeper  and  deeper,  making  bad  festering  sores. 
On  this  account  stockmen  hate  porcupines  and  usually 
shoot  them  on  sight.  In  the  lumber  regions  of  the  North 
porcupines  also  prove  a  nuisance,  —  in  another  way,  how- 
ever. They  gnaw  into  the  handles  of  axes,  oars,  or  any 
wooden-handled  implement,  especially  those  that  have  been 
used,  apparently  for  the  sake  of  the  salt  that  comes  from 
perspiration.  Hence  tools  are  not  left  lying  on  the  ground, 
but  axes  are  stuck  into  trees  with  the  handles  standing  far 
out,  oars  are  laid  up  in  bushes,  etc.  Porcupines  are  very 
stupid,  being  so  well  protected  by  their  spines  that  they 
do  not  need  to  use  their  wits  to  escape  an  enemy. 


262 


Descriptive  Zoology. 


Rats  and  Mice.  —  The  rats  and  mice  are  of  many  kinds 
and  of  vast  numbers.  Man  has  adopted  some  kinds  of 
animals,  but  these  creatures  may  be  said  to  have  adopted 
man.  They  are  universal  attendants  on  civilization  and 
are  as  cosmopolitan  as  man  himself.  The  length  of  time 
that  they  have  been  associated  with  man  is  hinted  at 
by  the  fact  that  the  word  for  mouse,  in  essentially  the 


FIG.  154.    CHIPMUNK. 

From  photograph  from  Recreation,  by  permission  of  G.  O.  Shields. 

same  form,  is  found  in  many  languages.  Though  they  have 
many  enemies  besides  man,  it  seems  impossible  to  exter- 
minate them,  for  they  are  protected  in  many  ways,  espe- 
cially by  their  nocturnal  habits,  and,  as  Coues  says,  by 
their  very  insignificance. 

Beavers.  —  The    largest    rodent    found   in   the   United 


Mammalia. 


263 


States  is  the  beaver.  It  has  webbed  hind  feet  and  a  broad, 
flat,  scaly  tail.  All  have  read  of  its  remarkable  intelli- 
gence and  skill  in  felling  trees  and  in  constructing  dams. 
It  was  formerly  widely  distributed,  but  is  now  rare,  owing 
not  merely  to  the  fact  that  it  has  been  trapped  for  its  fur, 
but  also  to  the  spread  of  civilization  itself. 

Squirrels.  —  The  squirrels  are  a  very  interesting  group, 
not  only  on  account  of  their  active  and  graceful  movements, 


FIG.  155.    COMMON  MOLE. 

but  also  on  account  of  their  human  trait  of  laying  up  pro- 
visions and  their  human  mode  of  eating.  Most  attractive 
are  the  tree  squirrels,  including  the  fox  squirrel,  the  gray 
squirrel,  the  red  squirrel,  and  the  flying  squirrel.  The 
woodchuck,  prairie  dog,  and  gophers  live  in  the  ground. 
The  true  gophers  have  large  cheek  pouches  in  which  they 
carry  out  the  soil  in  digging  their  burrows. 

The  Insect  Eaters.  —  This  order  is  best  represented  by 
our  common  mole,  whose  work  of  raising  a  ridge  of  sod  is 


264  Descriptive  Zoology. 

familiar  to  all.  They  make  these  ridges  in  burrowing  for 
earthworms  and  grubs,  which  are  their  main  food.  They 
are  well  fitted  for  digging  by  the  very  large  front  feet  and 
strong  muscles  of  the  front  legs.  Since  they  live  in  dark- 
ness, the  eyes  have  become  rudimentary,  sometimes  con- 
cealed by  the  skin.  The  teeth  are  like  those  of  a  diminu- 
tive flesh  eater.  The  nose  is  long,  bare  at  the  tip,  and  very 
sensitive.  There  are  no  external  ears.  The  shrews  are 
mouselike  and  are  probably  often  mistaken  for  mice,  as 
the  front  feet  are  not  enlarged  as  in  the  moles ;  but  the 
nose  is  more  pointed,  and  one  look  at  the  teeth  would  show 
that  a  shrew  is  not  a  "gnawer."  This  order  also  includes 
the  hedgehog  of  the  old  world,  which  has  the  hairs  devel- 
oped as  sharp  spines.  The  fact  that  both  the  hedgehog 
and  porcupine  have  sharp  spines  leads  to  confusion.  It  is 
unfortunate  that  many  writers  are  either  uninformed  or 
careless  in  this  matter  and  further  extend  an  already  wide- 
spread error.  The  two  animals  are  entirely  distinct,  and 
the  following  tabular  statement  may  aid  in  showing  their 
points  of  difference  :  — 

DIFFERENCES    BETWEEN    A   HEDGEHOG   AND    A 

PORCUPINE. 
HEDGEHOG.  PORCUPINE. 

Insectivora Order Rodentia 

Conical  points Teeth     .     .     .  Chisel-shaped  incisors 

Insects,  etc Food Herbage 

Not  barbed  }  ~      .    (•  •     •    Barbed 


Firmly  attached f  ^         } .     .     .     .       Loosely  attached 

Less  than  a  foot Size      ....      Two  feet  or  more 

Old  world Habitat  .     .    Both  old  world  and  new 

The  Bats.  —  The  bats  of  this  country  are  insectivorous, 
and  would  undoubtedly  be  classed  with  the  preceding 
order  if  they  were  not  flyers.  The  wing  is  a  fold  of  skin 


Mammalia. 


265 


supported  by  the  arm  and  the  excessively  elongated  fingers ; 
the  fold  in  our  bats  extends  to  and  includes  the  tail.  The 
thumb  is  free  from  the  wing  mem- 
brane and  has  a  hooked  claw  by 
which  the  bat  can  hang,  but  usually 
when  at  rest  it  hangs  head  down- 
ward by  the  hooked  claws  of  the 
hind  limbs.  Every  one  is  familiar 
with  the  flight  of  our  bats  as  they 
zigzag  after  insects.  Bats  are  chiefly 
nocturnal.  There  is  much  super- 
stition concerning  them.  There  are 
in  the  tropics  some  blood- 
sucking bats,  but  ours  ^ 
are  not  only  harmless  P 
but  beneficial.  Our  bats  <& 
hibernate  in  caves,  hoi-  ^ 
low  trees,  etc.  The  large  § 
bats  of  the  East  Indies,  > 
known  as  flying  foxes, 
are  fruit  eaters. 

The  Whales.  —  Though  living  con- 
tinually in  water,  whales  are  true 
mammals ;  they  bring  forth  their 
young  alive  and  nourish  them  by 
means  of  milk.  The  fore  limbs  are 
developed  into  flippers.  The  tail  is 
horizontally  flattened,  and  its  two 
lobes  are  called  flukes.  Whales  are 
devoid  of  hair.  The  whalebone  whale 
has  in  its  mouth  a  long  series  of 
fringed  baleen  plates  (whalebone),  which  serve  as  strainers. 
The  whale  ingulfs  whole  schools  of  crustaceans,  jelly- 


266  Descriptive  Zoology. 

fishes,  etc.,  and  the  water  passes  through  these  strainers 
and  out  at  the  sides  of  the  mouth.  Underneath  the  skin  is 
a  thick  layer  of  fat  which  furnishes  the  whale  oil.  Such  a 
layer  of  fat  protects  this  warm-blooded  animal  in  the  icy 
water  of  the  arctic  seas.  Since  the  discovery  of  our  oil 
fields  the  whale  fishery  has  declined.  The  "spouting"  of 
whales  is  not  due  to  a  column  of  water,  but  to  mucus  and 
the  condensed  moisture  of  the  breath. 

Whales  over  fifty  feet  long  are  not  often  taken,  though 
the  sperm  whale  is  sometimes  seventy-five  feet,  and  the 
"  sulphur-bottom,"  found  in  the  Pacific,  is  said  to  reach  even 
a  hundred  feet.  It  is  the  largest  living  animal.  Porpoises 
are  smaller  members  of  the  same  group. 

The  Sea  Cows.  —  Some  authors  class  these  with  the 
whales,  but  they  are  herbivorous  animals,  having  grinding 
molars  and  a  hairy  covering.  They  seem  to  stand  between 
the  whales  and  the  ungulates.  They  live  in  the  mouths  of 
large  rivers ;  the  manatee  is  found  in  Florida  and  on  the 
west  coast  of  Africa,  the  dugong  in  India  and  Australia. 
They  are  sometimes  killed  for  their  flesh,  which  is  said  to 
be  very  much  like  beef. 

The  Hoofed  Mammals.  —  The  horse  and  cow  may  stand 
as  examples  of  this  order,  the  ungulates.  The  hoofs  are 
excessive  developments  of  what  correspond  to  our  nails  or 
the  claws  of  other  animals.  In  many  forms  the  hoof  en- 
cases the  whole  of  the  lower  surface  of  the  foot.  It  appears 
to  be  a  special  adaptation  for  the  support  of  heavy  animals, 
many  of  which  have  to  run  rapidly  over  rough  or  even 
rocky  ground.  The  number  of  toes  is  typically  five,  though 
no  living  ungulate  has  more  than  four.  They  are  all 
digitigrade, — that  is,  they  walk  on  the  toes.  They  are  all 
herbivorous,  with  teeth  adapted  for  grinding.  This  is  a 
large  order,  and  its  members  are  of  a  large  average  size. 


Mammalia.  267 

In  its  domesticated  forms  it  is  probably  the  most  useful  of 
any  order  to  man,  as  from  it  are  derived  beasts  of  burden. 
Members  of  this  order  also  furnish  us  with  food  (meat,  milk, 
cheese,  butter),  leather,  etc.  The  domestication  of  the  horse, 
cattle,  sheep,  etc.,  dates  so  far  back  that  we  know  not  what 
were  the  wild  forms  from  which  they  have  descended.  The 
ungulates  are  divided  into  two  groups,  according  as  the 
number  of  toes  is  odd  or  even,  —  the  odd-toed  group  being 
called  Perrissodactyls,  and  the  even-toed,  Artiodactyls. 

The  Perissodactyls. —  These  forms  have  an  odd  number 
of  toes,  as  shown  in  the  horse,  rhinoceros,  and  tapir. 

The  Horse. — The  horses  now  in  this  country  are  not 
natives,  but  were  introduced  from  the  old  world;  the 
Indians  did  not  know  the  horse  till  after  what  we  call  the 
"  discovery  "  of  America.  Still,  America  did  have  horses 
in  earlier  geologic  periods,  and  the  history  of  the  develop- 
ment of  the  horse,  as  shown  by  fossil  remains  (largely 
found  in  this  country),  is  exceedingly  interesting.  The 
earliest  form  was  about  the  size  of  a  fox,  and  had  four 
well-developed  toes  in  front,  with  a  rudiment  of  a  fifth 
and  three  toes  behind.  Later  appears  a  form  with  four 
toes  in  front  and  three  behind.  Then  came  a  horse  about 
as  large  as  a  sheep,  with  only  three  fully  developed  toes 
in  front,  the  fourth  represented  by  a  rudiment,  but  still 
having  three  toes  in  the  hind  foot.  Later  still  the  outer 
toe  became  reduced  to  a  mere  remnant.  Then  came  a  form 
about  the  size  of  a  donkey,  with  three  toes  all  around ; 
the  middle  toe  persisting  and  the  two  on  each  side  becom- 
ing dwarfed.  Finally,  the  one-toed  horse  was  evolved,  the 
single  toe  being  the  middle  one  of  the  five,  that  is,  corre- 
sponding to  our  middle  toes  and  middle  fingers. 

The  Tapir.  —  The  tapirs  are  found  in  South  America 
and  Sumatra.  They  have  four  toes  in  front  and  three 


268 


Descriptive  Zoology. 


behind.    The  snout  is  prolonged,  suggesting  the  proboscis  of 

the  elephant,  but  its  relationship  is  plainly  with  the  hors'e. 

The   Rhinoceros.  —  The   rhinoceros    has   three   toes   all 


Mammalia.  269 

around.  It  is  peculiar  in  having  a  horn  on  the  top  of 
the  snout.  In  some  species  there  are  two  horns,  not  paired, 
however,  but  one  in  front  of  the  other.  These  animals  are 
found  in  Africa. and  East  India. 

The  Artiodactyls. — The  artiodactyls,  or  even-toed  un- 
gulates, have  either  two  or  four  toes.  These  are  symmetri- 
cally arranged  on  each  side  of  a  median  cleft ;  hence  they 
are  spoken  of  as  "  cloven-footed"  animals.  Lowest  among 
the  even-toed  ungulates  are  the  hippopotamus  and  the 
swine.  A  species  of  wild  hog,  the  peccary,  inhabits  Central 
and  South  America,  extending  into  Texas.  It  is  a  slender, 
active,  fearless  animal,  in  marked  contrast  to  our  inactive, 
fat-burdened  domestic  hog.  The  swine  are  omnivorous, 
the  other  ungulates  are  almost  strictly  herbivorous. 

Except  the  camel,  nearly  all  the  artiodactyls  have  four 
toes,  —  two  well  developed  and  two  rudimentary.  The  well- 
developed  toes  are  the  third  and  fourth,  the  first  toe  (cor- 
responding to  our  great  toe  and  thumb)  being  wanting. 
The  second  and  fifth  toes  are  small,  but  usually  with 
distinct  hoofs ;  they  are  shorter  and  back  of  the  two  main 
parts  of  the  hoof.  These  rudimentary  hoofs  are  commonly 
called  the  "  dewclaws."  They  do  not  ordinarily  reach  the 
ground,  and  are  of  little  if  any  use,  except  in  the  reindeer. 

The  Ruminants.  —  With  the  exception  of  the  hippopota- 
mus and  the  swine,  all  the  even-toed  ungulates  are  cud 
chewers  and  have  complex  stomachs.  As  an  example,  let 
us  consider  the  cow.  There  are  no  upper  incisors ;  grass 
and  herbage  are  bitten  or  broken  off  by  pressing  the  lower 
incisors  against  the  hard,  toothless  pad  of  the  upper  jaw. 
The  molars  are  well  developed,  and  the  lateral  chewing 
motions  of  the  jaw  are  well  known.  In  keeping  with  this 
lateral  motion,  the  ridges  on  the  crowns  of  the  molars  run 
lengthwise  in  wavy  lines.  The  stomach  consists  of  four 


270 


Descriptive  Zoology. 


compartments.  When  the  food  is  cropped  it  is  swallowed 
without  chewing.  It  passes  into  the  large  paunch,  or  first 
stomach ;  when  the  ruminant  lies  down  to  rest,  the  soaked 
fodder  is  passed  into  the  small  second  stomach,  the  honey- 
comb or  reticulum,  where  it  is  formed  into  distinct  masses 
and  returned  to  the  mouth  for  thorough  mastication.  It 
again  goes  down  the  gullet,  this  time  to  the  third  stomach, 
the  psalterium,  or  manyplies,  whence  it  enters  the  true 
stomach,  or  fourth  stomach,  sometimes  called  the  rennet. 

The  intestine  is  very  long,  be- 
tween twenty  and  thirty  times 
the  length  of  the  body.  The 
ruminants  need  a  large  quantity 
of  food,  hence  it  is  easy  to  see 
how  it  is  of  advantage  to  them 
to  be  able  to  gather  their  food 
quickly,  retire  to  a  place  of  con- 
cealment, and  digest  it  at  their 
leisure,  as  many  of  them  are 
comparatively  defenseless.  The 
males  of  all  the  ruminants,  except 
the  camels,  have  horns,  and  in 
many  species  the  females  also 
possess  them,  though  usually  much  smaller  than  those  of  the 
male. 

The  Hollow-horned  Ruminants.  —  In  cattle,  sheep,  goats, 
and  antelopes,  the  horn  consists  of  a  bony  core,  covered 
with  a  layer  of  horn,  which  is  not  shed  except  in  the  case 
of  the  pronghorn  antelope  of  our  Western  plains. 

Sheep.  —  The  rams  have  large,  curved  horns,  which  they 
use  for  butting  when  fighting.  Our  native  sheep  is  the 
Rocky  Mountain,  or  bighorn  sheep,  so  named  from  its 
immense  horns.  These,  in  the  old  rams,  become  very  much 


FIG.  158.      t>IAGRAM   OF  THE 

STOMACH  OF  A  RUMINANT. 

Showing  the  course  of  the  food. 

From   Kingsley's   Comparative 

Zoology. 


Mammalia. 


271 


battered.  Hence  arose  the  story,  long  widely  accepted, 
that  they  jump  down  precipices,  alighting  on  their  horns. 
Since  the  ewes  and  lambs  can  go  anywhere  the  rams  can, 
the  absurdity  of  the  account  is  evident.  They  are  remark- 


Lamb  Ram.  Ewe. 

FIG.  159.    MOUNTAIN  SHEEP  FAMILY. 

From  photograph  of  some  of  the  author's  trophies. 

able  climbers,  walking  securely  on  a  narrow  ledge,  perhaps 
over  a  sheer  precipice  of  a  thousand  feet,  with  the  utmost 
unconcern.  They  are  wary  animals,  usually  having  a  sen- 


272  Descriptive  Zoology. 

tinel,  commonly  an  old  ram,  posted  on  a  high  point  of  rock, 
on  the  lookout  for  enemies.  They  seem  to  expect  attack 
from  below,  so  the  hunter  tries  to  get  above  them.  They 
stay  most  of  the  time  above  timber  line. 

Goats.  —  The  Rocky  Mountain  goat  dwells  in  equally 
inaccessible  mountain  tops.  Its  color  is  pure  white,  though 
its  coat  is  usually  dingy  from  the  habit  of  sunning  itself  in 
a  bed  of  dust.  Its  white  coat  seems  odd  for  a  wild  animal. 
But  when  one  sees  it  in  its  home,  up  among  snow  banks 


FIG.  160.    ROCKY  MOUNTAIN  GOAT. 

From  photograph  of  specimen  mounted  by  L.  L.  Dyche,  in  Camp  Fires  of  a  Naturalist. 
By  permission  of  D.  Appleton  &  Co. 

and  light-colored  rocks,  it  seems  well  adapted  to  its  sur- 
roundings. It  has  small,  smooth,  black  horns.  Mountain 
goats  are  rather  stupid  animals.  The  main  difficulties 
in  hunting  them  are  due  to  the  steepness  of  ascent  and 
the  rarefied  condition  of  the  air. 

The    Buffalo.  —  The    American    bison,    usually    called 
"  buffalo,"  is  now  nearly  extinct.     Buffaloes  once  roamed 


Mammalia. 


273 


in  countless  herds  over  the  plains  and  prairies  of  almost 
all  of  the  United  States;  to-day  probably  the  only  wild 
herd  in  the  country  is  in  the  Yellowstone  Park,  and  it 
numbers  hardly  more  than  fifty.  There  are  probably  a 
limited  number  in  British  Columbia.  Once  the  mainstay 
of  the  Indians,  furnishing  them  with  food,  clothing,  and 
tents  (tepees),  they  were 
doomed  to  give  way  before 
an  advancing  civilization. 

The  Antelope. — The  prong- 
horn,  or  antelope  of  our 
Western  plains,  is  a  peculiar 
animal,  the  only  member  of 
its  family.  It  stands  be- 
tween the  cattle  and  the 
deer  families.  It  has  hol- 
low horns,  which  are  shed 
annually.  The  bony  core  is 
a  projection  from  the  skull 
and  is  never  shed.  It  is 
very  swift-footed  and  wary, 
keen  of  eye  and  nose.  Like 
most  of  our  wild  ruminants, 
it  has  a  white  rump.  When 
hunted  it  usually  runs  to  a  ridge  and  stops  to  watch. 
Instead  of  getting  out  of  sight  of  its  pursuer,  its  policy 
is  to  keep  its  enemy  in  sight,  but  at  a  safe  distance. 
The  antelope  is  rapidly  disappearing  and  is  doomed  to 
extermination. 

The  Solid-horned  Ruminants  —  Deer. — The  deer  family  in 
this  country  includes  three  species  of  deer,  and  the  elk, 
moose,  and  caribou.  Except  in  the  caribou,  only  the  males 
have  horns.  The  horns,  which  are  solid,  are  shed  annually, 


FIG.  161.    ANTELOPE. 

From  Forest  and  Stream. 


274 


Descriptive  Zoology. 


usually  in  December  or  January.  They  grow  out  again, 
with  an  added  prong  for  each  of  the  first  six  or  eight  years. 
Till  fully  grown  the  horns,  or  antlers,  as  they  are  often 
called,  are  covered  with  a  soft  fur,  and  are  said  to  be  "  in 
the  velvet."  When  the  horns  are  mature  this  skin  dies 


FIG.  162.    WHITETATL  DEER.    HORNS  IN  THE  "  VELVET.' 

From  Recreation,  by  permission  of  G.  O.  Shields. 

and  peels  off,  the  owner  assisting  by  rubbing  them  against 
shrubs  and  small  trees.  The  two  common  species  of  deer 
are  the  whitetail  and  the  blacktail  deer.  The  whitetail 
deer  is  probably  identical  with  the  Virginia  deer  or  red 
deer.  It  is  the  most  widely  distributed  form,  extending 
from  Maine  to  Florida,  and  westward  to  the  Rocky  Moun- 


Mammalia. 


275 


tains,  usually  keeping  in  lowlands.  The  term  "red  deer" 
is  inappropriate,  as  all  our  deer  are  red  when  in  their 
summer  coat,  turning  grayish  in  the  fall.  The  blacktail 
is  Western,  preferring  mountains  or  hilly  country.  The 
tip  of  the  tail  is  black.  This  deer  is  also  called  "  mule 
deer,"  on  account  of  its  very  large  ears.  The  horns  of  the 


FIG.  163.    BLACKTAIL  DEER. 

From  Forest  and  Stream. 

two  species  branch  differently  (see  Figs.  162  and  163). 
The  elk  (see  Frontispiece)  is  larger  than  the  other  deer, 
sometimes  weighing  eight  hundred  and  perhaps  a  thousand 
pounds.  A  bull  elk  surpasses  any  of  the  stags  of  the 
old  world.  Elk  are  being  reduced  in  number  and  bid  fair 
to  be  exterminated,  since  they  cannot  hide  so.  cunningly 
as  deer. 


276 


Descriptive  Zoology. 


The  deer  family  is  peculiar  in  lacking  the  bile  sac. 
Deer  shed  their  coats,  in  the  summer  time  being  reddish, 
or  "in  the  red,"  as  the  hunters  say;  while  in  the  winter 
they  are  grayish,  or  "in  the  blue."  In  the  summer  the 
males  of  the  elk  and  deer  keep  by  themselves,  ranging 


FIG.  164.    MOOSE. 

From  Forest  and  Stream. 

high  on  the  mountain  sides,  often  upon  the  rocks  near 
timber  line,  while  the  does  and  fawns  are  more  likely  to  be 
found  on  lower  slopes  or  in  the  valleys. 

In  hunting  squirrels,  the  hunter  has  only  two  senses  to 
guard  against,  sight  and  hearing.     But  in  hunting  deer  the 


Mammalia.  277 

hunter  must  not  only  keep  out  of  sight  and  out  of  hearing, 
but  must  also  avoid  detection  by  a  third  sense,  —  that  of 
smell.  If  he  attempts  to  approach  this  game  from  the 
windward  side,  they  are  almost  sure  to  detect  him  and  to 
escape,  often  without  his  being  aware  of  their  presence, 
unless  he  afterward  discovers  their  tracks. 

The  moose  is  an  awkward-looking  animal,  with  its  long 
hump  nose.  The  antlers  are  spread  out  into  a  flattened 
"  blade  "  near  the  tips.  The  moose  lives  in  marshy  for- 
ests. There  is  a  considerable  number  in  northern  Maine, 
Nova  Scotia,  Alaska,  and  in  British  Columbia.  A  few 
remain  in  Idaho,  in  the  northwestern  part  of  Montana,  and 
in  the  region  of  Yellowstone  Park.  The  moose  and  deer 
feed  almost  entirely  on  twigs  and  leaves,  that  is,  they 
"browse,"  while  elk  feed  to  a  considerable  extent  on  grass, 
like  our  domesticated  cattle. 

The  Camel.  —  The  camel  has  but  two  toes,  with  large, 
soft  pads.  The  hump  is  a  storehouse  of  fat.  They  can 
go  without  water  longer  than  most  animals,  but  this  is  no 
more  than  might  be  expected  of  an  animal  accustomed 
to  living  in  a  desert  country. 

The  Giraffe.  — The  giraffe  is  remarkable  for  the  extreme 
length  of  its  neck.  Nevertheless,  it  has  but  seven  cervical 
vertebrae,  the  same  number  that  we  have,  the  increase 
being  due  to  the  lengthening  of  the  individual  vertebrae. 

The  Elephants.  —  The  elephants  are  essentially  ungu- 
lates, having  five  toes,  each  incased  in  its  own  hoof;  but 
on  account  of  the  peculiar  development  of  the  nose  into  a 
trunk,  or  proboscis,  most  authors  place  them  in  a  separate 
order.  The  excessively  long  snout  is  flexible,  very  muscu- 
lar, and  serves  as  a  hand  in  conveying  food  to  the  mouth. 
This  arrangement  seems  especially  desirable  for  an  animal 


278  Descriptive  Zoology. 

with  long,  stiff  legs  and  a  very  short  neck.  Even  if  he 
were  not  stiff-legged  and  short-necked,  it  would  be  incon- 
venient for  him  to  dispense  with  the  trunk  so  long  as  he 
retains  the  tusks.  These  are  the  long  upper  incisors, 
which  are  of  solid  ivory,  the  slight  amount  of  enamel 
which  originally  covered  the  tips  soon  wearing  away. 
Elephants  are  herbivorous  and  have  one  large  grinding 
tooth  in  each  half-jaw.  The  skull  is  not  heavy  in  proportion 
to  its  size,  as  it  has  many  large  air  spaces.  The  skin  re- 
tains a  few  scattered  hairs,  with  a  distinct  tuft  at  the  end 
of  the  tail.  Two  species  of  elephants  are  found,  one  in 
India,  the  other  in  Africa.  Still  larger  than  the  elephants 
were  their  (now  extinct)  relatives,  the  mastodon  and  the 
mammoth. 

The  Flesh  Eaters.  —  The  flesh  eaters,  or  beasts  of  prey, 
are  fitted  for  their  life  (i)  by  their  activity;  (2)  by  their 
sharp  teeth,  especially  the  long  canines;  (3)  by  the  claws, 
usually  sharp  and  strong ;  (4)  by  their  color,  usually  in  har- 
mony with  their  surroundings.  The  lower  jaw  is  so  hinged 
that  only  an  up-and-down,  or  true  hinge  motion,  is  per- 
mitted ;  this  should  be  considered  in  comparison  with  the 
lateral  jaw  movements  of  ungulates  and  the  gliding  for- 
ward-and-back  of  the  rodents.  Instead  of  being  flat-topped, 
the  molars  are  somewhat  like  saw-teeth,  the  upper  and 
lower  shutting  past  each  other  like  shear  blades.  The 
flesh  eaters  have  simple  stomachs  and  relatively  short  in- 
testines, as  the  digestion  of  flesh  is  short  and  easy  as  com- 
pared with  that  of  vegetable  food.  The  senses  are  generally 
very  acute.  As  there  is  considerable  variation  in  adapta- 
tion to  the  conditions  of  life,  let  us  consider  four  types  of 
flesh  eaters  as  represented  by  the  cat,  dog,  bear,  and  seal. 

The  Cats.  — Cats  are  distinguished  from  the  other  beasts 
of  prey  by  having  the  claws  retractile,  that  is,  they  can  be 


Mammalia.  279 

withdrawn  into  a  sheath,  where  they  are  kept  most  of  the 
time,  the  animal  walking  on  pads  developed  on  the  next  to 
the  last  joint  of  each  toe.  These  pads  enable  the  cats  to 
walk  noiselessly,  and  this  is  an  important  trait,  as  they 
capture  their  prey  by  lying  in  wait  or  by  creeping  near  it 
stealthily,  then  suddenly  pouncing  upon  it.  In  a  bright 
light  the  pupils  are  reduced  to  a  narrow  vertical  slit.  In 
the  dark  they  dilate  widely ;  thus  they  are  fitted  for  their 
nocturnal  habits. 

Our  biggest  cat  is  the  cougar  or  puma,  also  called  the 
American  panther,  and  in  the  West  known  altogether  as  the 
mountain  lion.  Its  body  is  about  as  thick  as  that  of  a 
sheep  and  somewhat  longer,  with  a  long  tail.  It  is  tawny 
brownish  yellow  above,  paler  beneath.  Though  fierce 
when  wounded  or  cornered,  it  is  a  sneaking,  cowardly 
creature,  few  instances  being  known  of  its  attacking  a 
human  being.  It  follows  mountain  sheep  and  other  mam- 
mals, ready  to  seize  the  young  or  the  sickly  or  wounded 
adults.  It  is  found  from  British  Columbia  to  Patagonia. 
The  wild-cat  and  lynx  are  smaller  and  are  short-tailed, 
being  in  some  localities  called  "  bobcats."  Other  cats  are 
the  lion,  tiger,  leopard,  jaguar,  etc. 

The  Dogs.  —  Dogs  have  the  nose  more  pointed  than  the 
cats.  The  claws  are  blunt  and  not  retractile.  The  dog- 
like  form  includes  the  wolves,  jackals,  and  foxes.  Most 
of  this  group  capture  their  prey  by  running  it  down,  instead 
of  by  stealth  as  in  the  cat  tribe,  though  the  fox  is  rather 
catlike  in  this  respect  Proverbial  for  his  cunning,  the 
fox  remains  in  thickly  settled  districts,  not  disdaining  birds 
that  are  domesticated.  We  have  two  species  of  wolves. 
The  prairie  wolf,  or  coyote,  has  a  sneaking,  cowardly  dis- 
position. When  an  Indian  wishes  to  express  his  utmost 
contempt  for  an  individual  he  calls  him  a  coyote.  The 


280 


Descriptive  Zoology. 


timber  wolf  is  larger  and  does  considerable  injury  by  kill- 
ing calves  and  lambs.  A  bounty  is  paid  for  wolf  scalps. 
Wolves  are  little  to  be  feared  in  this  country. 

The  hyenas  are  between  the  cats  and  the  dogs.     They 
have  heavy  shoulders  and  fore  limbs,  also  strong  jaws  and 


FIG.  165.    GRIZZLY  BEAR,  FROM  PHOTOGRAPH. 

From  Recreation,  by  permission  of  G.  O.  Shields. 

teeth  to  crush  bones.  They  are  the  scavengers  among 
the  beasts  of  prey,  like  the  vulture  among  the  birds  of 
prey. 

Both  the  cats  and  the  dogs  walk  on  the  toes,  hence  are 
said  to  be  digitigrade. 

The  Bears.  —  Bears  walk  on  the  whole  flat  of  the  foot  and 
are  therefore  called  plantigrade.  Bears  are  less  distinctly 
carnivorous  than  the  above  groups.  They  live  largely  on 
berries  when  they  can  get  them.  They  eat  many  insects, 


Mammalia.  281 

turning  over  logs  and  stones  and  devouring  the  beetles, 
worms,  and  larvae.  They  are,  in  fact,  omnivorous  and 
not  only  in  their  food,  but  in  their  mode  of  feeding,  re- 
semble hogs.  The  ferocity  of  bears  is  greatly  exaggerated. 
They  are  extremely -shy  animals,  usually  on  the  lookout 
for  danger ;  even  when  feeding  they  look  around  at  short 
intervals.  One  common  mode  of  hunting  them  is  to  watch 
a  carcass  of  some  large  animal.  When  a  bear  discovers 
such  a  "feast"  he  feeds  greedily,  and  either  stays  in  the 
neighborhood  or  returns  regularly  till  it  is  all  consumed. 
The  hunter  lies  in  wait  or  approaches  when  the  bear  is 
feeding,  usually  at  dawn  or  at  dusk.  The  approach  must 
be  made  with  the  utmost  care  from  the  leeward,  or  the  bear 
is  gone  without  being  seen.  A  bear  has  no  wish  to  culti- 
vate man's  acquaintance.  But  a  wounded  bear  is  a  most 
desperate  and  dangerous  foe.  He  is  quick  on  his  feet  and 
strikes  like  a  prize  fighter,  a  single  blow  from  his  mighty 
arm,  with  its  long  claws,  often  completely  disemboweling 
a  victim.  In  rare  instances  a  bear,  when  discovered  feed- 
ing, becomes  enraged  and  shows  fight.  Aside  from  these 
conditions  almost  the  only  occasion  when  a  bear  "  begins 
a  fight "  is  when  a  female  with  cubs  is  met ;  even  then  she 
often  ignominiously  takes  to  flight.  Though  clumsy  in 
appearance,  the  bear  is  a  swift  runner.  In  the  fall  bears 
usually  become  very  fat.  Through  most  of  the  winter  they 
hibernate,  or  "hole  up,"  as  the  hunters  say,  in  a  cave  of 
rocks  or  under  the  roots  of  a  big  tree.  North  America 
has  four  kinds  of  bears:  the  polar  bear;  the  grizzly, 
including  the  silvertip ;  the  black  bear,  including  the  cin- 
namon bear ;  and  the  big  brown  bear  of  Alaska. 

The  raccoon  is  very  mudi  like  a  diminutive  bear,  not 
only  in  its  plantigrade  feet,  but  also  in  its  food  habits. 
Coons  are  shrewd  creatures,  and  make  good  pets. 


282  Descriptive  Zoology. 

The  Weasels.  —  These  are  by  some  placed  with  the  bears, 
while  others  ally  them  to  the  cats.  In  this  family  are  the 
weasel,  mink,  ermine,  marten,  ferret,  otter,  badger,  wolver- 
ine, skunk.  All  are  valuable  for  their  fur.  The  weasel 
turns  white  in  winter.  Most  of  these  have  strong  scent 
glands.  Several  of  them  are  excellent  swimmers  and 
divers,  living  largely  on  fish.  One  otter  lives  in  the  sea. 

The  Seals.  —  The  seals  are  fitted  for  aquatic  life  by  hav- 
ing the  hands  and  feet  developed  as  paddles  or  "  flippers," 
the  limbs  being  very  short.  The  sea  lion  can  walk  on  all 
fours ;  others  have  the  hind  limbs  permanently  turned 
backward,  forming  a  sort  of  "tail  fin,"  so  that  they  swim 
very  much  like  the  fishes,  on  which  they  feed.  Seals  are 
sometimes  said  to  be  pinnigrade  (walking  by  fins)  in  con- 
trast to  the  digitigrades  and  plantigrades.  No  seals  in- 
habit the  tropics.  The  seal  grounds  of  the  southern 
hemisphere  have  been  depleted  by  indiscriminate  killing, 
and  the  northern  fields  bid  fair  to  meet  the  same  fate. 

The  Primates. — This  order,  highest  of  all  the  mam- 
mals, includes  the  monkeys,  apes,  and  man.  There  is  a 
great  range  from  the  little  squirrel-like  marmoset  to  the 
massive  gorilla,  and  from  the  horizontal-bodied,  four-footed  . 
lemur  to  the  erect  biped,  man.  But  structure  is  the  basis 
of  classification,  and  many  of  these  lower  forms  have 
almost  bone  for  bone  and  muscle  for  muscle  similar  to 
those  of  man.  The  higher  apes  are  tailless.  The  form 
differs  greatly,  the  facial  angle  of  the  ape  being  almost 
that  of  a  dog,  while  the  Caucasian  has  an  angle  of  about 
95°.  As  we  approach  man  in  the  scale  the  body  becomes 
more  erect  and  is  supported  on  the  flat  sole,  instead  of  on 
the  outer  edges  as  in  the  lower  forms.  Man  alone  has  a 
well-developed  hand,  and  he  distances  all  other  forms  in 
having  the  power  of  speech,  although  some  authors  think 


Mammalia. 


Duodenu 


apes  have  a  language.  The  name  orang-utan  means  "  man 
of  the  woods."  Anatomists  do  not  agree  as  to  which  is 
nearer  man,  the  chimpanzee  or  the  gorilla.  It  must  be 
borne  in  mind  that  in  the  animal  world  classification  is 
based  on  structure,  and  that  the  zoological  point  of  view 
does  not  take  into  con- 
sideration the  intellectual,  Gullct 
moral,  or  spiritual  quali-  stomach 
ties. 

Characteristics  of  Mam- 
mals.— (i)  Mammals  have 
a  hairy  covering.  (2)  The 
young  are  born  alive. 
(3)  The  young  are  nour- 
ished by  milk  from  mam- 
mary' glands.  (4)  There 
is  a  diaphragm  separating 
the  body  cavity  into 
thorax  and  abdomen. 
(5)  All  have  teeth  set  in 
sockets.  (6)  Two  pairs  of 
limbs  are  usually  present. 

(7)  There    are    usually 
seven   cervical    vertebrae. 

(8)  The  lower  jaw  articu- 
lates   directly    with     the 
skull  and  not  by  the  inter- 
vention of  a  separate  bone 

(quadrate  bone)  as  in  birds.  (9)  There  is  an  epiglottis 
covering  the  opening  (glottis)  to  the  windpipe.  (10)  The 
blood  is  warm,  and  of  a  nearly  constant  temperature. 
(11)  The  heart  is  completely  divided  by  a  partition  into 
right  and  left  halves. 


FIG.  166. 


Rectum 


STOMACH  AND  INTESTINES 
OF  MAN. 


284 


Descriptive  Zoology. 


CLASSIFICATION   OF   MAMMALS. 


SUBCLASSES. 


ORDERS. 


2.  Theria^j     (Placentals) 


i.    Prototheria i.    Monotremata  —  Duckbill    and'  Spiny  Ant-eater 

f  (Nonplacentals]   .   2.   Marsupialia Opossum,  Kangaroo 

3.  Edentata Sloth,  Armadillo 

4.  Rodentia Rabbit,  Squirrel 

5.  Insectivora Mole,  Shrew 

6.  Cheiroptera Bat 

7.  Cetacea Whale,  Porpoise 

8.  Sirenia ; Sea  Cow 

9.  Ungulata Horse,  Cow,  Deer 

10.  Proboscidea Elephant 

11.  Carnivora Cat,  Dog,  Bear,  Seal 

12.  Primates Lemur,  Ape,  Man 

CHARACTERISTICS   OF   CHORDATA. 

1.  There  is  a  notochord,  a  long  skeletal  rod,  a  sort  of 
forerunner  of  the  backbone. 

2.  There  are  gill  slits  opening  from  the  throat  to  the 
outside. 

3.  The  central  nervous  system  is  a  hollow  tube  and  is 
wholly  dorsal  to  the  digestive  tube. 

CHARACTERISTICS  OF  VERTEBRATA. 

In  the  Vertebrata  the  characters  given  for  the  Chordata 
are  distinctly  displayed,  and  a  permanent  backbone  is  de- 
veloped. A  cross  section  of  a  vertebrate  shows  two  cavities 
(see  Fig.  150),  the  dorsal  containing  the  cerebro-spinal 
nervous  system,  and  the  ventral  containing  the  digestive, 
circulatory,  and  respiratory  organs.  In  the  vertebrates  a 
liver  is  always  present.  The  nervous  system  is  usually 
well  developed. 

Classification  of  Animals.  —  An  early  classification  divided 
animals  into  two  groups,  the  vertebrates,  or  the  animals 
having  backbones ;  and  the  invertebrates,  those  lacking  a 


Mammalia. 


backbone.  A.  comparatively  recent  grouping  is  into  Pro- 
tozoa, or  one-celled  animals,  and  Metazoa,  or  many-celled 
animals.  Each  of  these  groupings  simply  characterizes 
one  group  (one  system  taking  the  lower  end  and  the  other 
the  higher  end  of  the  animal  series)  and  lumps  off  all  the 
rest  in  one  negatively  named  group.  Neither  of  these  sys- 
tems pretends  to  do  anything  more  than  call  attention  to 
the  presence  or  absence  of  a  single  feature  of  structure. 


Fish 


Toad 


Snake 


Sparrow 


Mouse 


Olfactory 

lobe         —? 
Cerebrum 

Mid  brain   - 


Cerebellum 
Spinal  bulb    

Spinal  cord     .. 

FIG.  167.    DIAGRAM  OF  BRAINS  OF  VERTEBRATES. 

From  Kellogg's  Zoology. 

The  Basis  of  Classification  of  Animals.— The  basis  of  classi- 
fication of  animals  is  structure,  only  so  many  branches  being 
recognized  as  there  are  distinct  plans  of  structure.  It  is 
generally  understood  that  the  structure  considered  is  that  of 
the  adult,  since  many  animals  change  greatly  during  their 
development.  But  in  some  cases,  especially  of  degenerate 
forms,  the  larval  form  shows,  more  clearly  than  the  adult, 
the  true  relationship.  Consequently  embryology  must  be 
called  in  as  an  aid  in  classification.  Fossils  also  clear  up 
many  doubtful  points  in  classification. 


CHAPTER   XVIII. 
BRANCH   PROTOZOA. 

THE   ONE-CELLED   ANIMALS. 

Amoeba.  —  The  Proteus  Animalcule.  —  One  of  the  sim- 
plest -forms  of  animal  life  is  the  Amoeba.  It  is  found  in 
the  slimy  coating  usually  found  on  submerged  leaves  and 
stems  in  standing  water,  or  in  the  slimy  ooze  resting  on 
the  mud  at  the  bottom.  If  this  ooze  be  examined  under 
a  high  power  of  a  microscope,  amoebae  may  usually  be 
found,  though  occasionally  one  has  to  search  for  some  time 


Endoplasm 


Ectoplasm 


Pseudopods 
extending 


Pseudopods 
retracting 


Contractile  vacuole 


Water  vacuoles 


Food  vacuoles 

FIG.  168.    AMCEBA. 

before  he  is  successful.  And  it  is  difficult  for  a  begin- 
ner to  be  certain,  at  first,  whether  what  he  has  found  is 
really  an  amoeba.  An  amoeba  is  a  speck  of  clear,  color- 
less, jellylike  substance  called  protoplasm,  with  a  distinct/ 
though  delicate,  outline.  There  can  usually  be  discerned  a 
clearer  outer  layer,  the  ectoplasm,  and  a  more  Dotted  cen- 
tral portion,  the  endoplasm ;  but  there  is  nfl  distinct  line 
between  the  two.  Sometimes  one  can  see  a  more  dense 

286 


Protozoa. 


287 


appearing  portion,  the  nucleus,  and  occasionally  there  ap- 
pears a  clear  space,  the  contractile  vacnole. 

If  the  object  is  an  amoeba,  it.  will  usually  soon  betray 
itself  by  its  motion.  First  there  is  a  bulging  out  on  one 
side,  and  this  projection  may  be  prolonged  into  a  distinct 
lobe,  called  a  pseudopod.  The  amoeba  may  form  several 
of  these  pseudopods  at  the  same  time,  so  that  it  may  have 
little  central  body  and  nearly  all  of  its  substance  may  be 
in  the  pseudopods  These  pseudopods  may  be  extended 
and  retracted  without  changing  the  place  of  the  amoeba. 
But  more  often  after  a  pseudopod  has  been  protruded,  the 
vest  of  the  body  follows  it,  seeming  to  flow  into  it ;  by 


'•-<.*3$3JJ 
FIG.  169.    AMOZBA:  CHANGES  IN  FORM,  DRAWN  AT  SHORT  INTERVALS. 

repetition  of  this  process  the  amoeba  changes  its  place, 
and  thus  exhibits  not  only  motion,  but  locomotion.  If 
watched  for  some  time  the  amoeba  may  be  seen  to  change 
its  shape  considerably  and  to  make  slow  progress,  some- 
times for  a  considerable  time  in  the  same  direction. 

Patient  watching  may  reveal  how  the  amoeba  takes  its 
food.  If  a  small  plant  or  animal  cell  or  portion  of  such 
matter  lies  in  its  way,  a  pseudopod  is  pressed  against  it 
and  it  becomes  embedded  in  the  endoplasm.  With  any 
such  food  material  there  is  usually  taken  a  small  amount 
of  water.  The  space  occupied  by  the  .water  and  absorbed 
food  is  called  a  food  vacuole.  Usually  a  number  of  these 
food  vacuoles  may  be  seen  in  an  amoeba  After  a  time  the 
water  and  other  matter  disappear,  having  been  digested 
and  absorbed  and  assimilated  into  the  substance  of  the 


288  Descriptive  Zoology. 

amoeba.  Occasionally  a  grain  of  sand,  or  other  indiges- 
tible matter,  is  taken  in ;  in  this  case  it  is  finally  passed 
out  of  the  body,  usually  being  left  behind  as  the  amoeba 
moves  on.  There  is  no  mouth ;  food  may  be  taken  in  at 
any  part  of  the  surface.  There  is  no  stomach  ;  the  space 
occupied  by  the  ingested  food  is  an  improvised  stomach. 
There  is  no  anus,  residual  matter  being  passed  out  at  the 
point  most  convenient.  Still,  as  the  amoeba  moves  about 
in  search  of  food,  the  surface  that  happens  to  be  foremost 
is  likely  to  take  in  the  new  matter,  and  the  part  that  is, 
for  the  time,  rearmost  serves  as  the  place  of  exit.  The 
amoeba  may  be  said  to  flow  around  its  food,  and  to  flow 
away  from,  and  so  leave  behind,  its  waste  matter. 

The  work  of  moving  about  involves  the  expenditure  of 
energy.  This  energy  is  produced  by  the  oxidation  of  the 
substance  constituting  the  amoeba.  Oxygen  is  constantly 
being  absorbed  through  the  surface  to  supply  this  need, 
which  varies  according  to  the  degree  of  activity.  The  oxi- 
dation of  the  matter  of  the  body  of  the  amoeba  produces 
carbon  dioxid  and  water,  which  are  passed  off,  invisibly, 
through  the  surface.  The  new  food  taken  replaces  the  loss 
by  such  oxidation.  This  taking  in  of  oxygen  and  giving 
out  carbon  dioxid  is  respiration,  in  its  simplest  form.  In 
the  oxidation  heat  is  produced,  which  probably  is  given 
off  to  the  water  about  as  fast  as  it  is  produced  in  excess 
of  the  temperature  of  the  surrounding  medium.  Actively 
moving  amoebae  warm  the  water  in  which  they  move,  as 
truly  as  we  warm  the  water  in  which  we  are  bathing, 
or  the  air  in  which  we  are  performing  active  muscular 
work.  And  as  we  taint  the  air  with  our  waste  products 
and  need  a  constant  renewal  of  the  surrounding  air,  so 
the  amoeba  must  not  be  confined  too  closely  in  a  limited 
quantity  of  water  that  is  sealed  from  the  air. 


Protozoa. 


289 


The  amoeba  shows  that  it  has  a  sense  of  touch,  for  it 
frequently  avoids  solid  objects  with  which  it  comes  into 
contact,  passing  to  one  side.  It  has  the  characteristic 
termed  irritability.  This  characteristic  does  not  involve 
any  special  degree  of  sensitiveness,  but  simply  the  power 
to  receive  impressions  through  contact  with  external  objects. 
If  stimulated  by  slight  electric  shocks,  the  amoeba  may 
be  made  to  withdraw  its  pseudopods  and  remain  quiet 
in  a  spherical  form.  It  is  said  to  have  contracted,  and 
is  said  to  be  endowed  with  the  property  of  contractility, 
but  it  is  simpler  merely  to  say  that  it  has  changed 
its  form. 

But  the  amceba  does  not  always  wait  to  be  stimu- 
lated from  without  to  make  it  move.  It  sometimes 
appears  to  move  "  of  its  own  accord,"  as  we  say.  That 
is,  it  is  automatic,  in  the  sense  of  self-moving. 


,   mm 

FIG.  170.    AMCEBA  DIVIDING. 


,,, 


If  amoebae  are  well  nourished,  they  are  likely  to  mul- 
tiply. They  do  this  by  simple  division.  An  amoeba 
becomes  constricted  in  the  middle.  The  constriction 
increases  until  the  individual  is  divided  into  two. 

Encysted  Amoeba.  —  Sometimes  an  amoeba,  when  sub- 
jected to  drouth,  or  perhaps  other  unfavorable  conditions, 
forms  a  tough  outer  wall,  and  remains  in  a  quiet  condi- 
tion. The  tough  covering  is  called  a  "cyst,"  and  the 
amoeba  is  said  to  be  "encysted."  It  may  thus  remain 


290  Descriptive  Zoology. 

dormant  for  a  long  time,  until  more  favorable  conditions 
return,  when  it  ruptures  the  cyst,  crawls  out,  and  once 
more  renews  its  former  active  life. 


SUMMARY  OF   THE   CHARACTERISTICS   OF  AMCEBA 

1.  It  eats ;  it  takes  in  material  through  its  surface  from 
the  surrounding  water. 

2.  It  digests ;  the  material  thus  taken  in  is  made  soluble 
so  that  it  can  be  used  in  building  up  the  body  of  the  amoeba. 

3.  It  assimilates ;  after  suitable  preparation  the  mate- 
rial is  taken  into  the  actual  substance  of  the  amoeba ;  it  is 
"made  like,"  as  the  word  "assimilate"  signifies. 

4.  It  grows,  as  a  result  of  assimilation.     Growth  is  the 
increase  in  size  and  substance  of  a  living  thing  as  a  result 
of  taking  material  from  the  outside  and  making  it  over 
into  its  own  body.     Growth  should  be  distinguished  from 
the  mere  increase  in  size  of  such  dead  objects  as  an  icicle 
or  a  crystal  by  the  accretion   of   more   material   on   the 
outside. 

5.  It  moves ;  it  has  power,  not  to  change  its  bulk,  but 
to  change  its  shape.     It  is  able  to  rearrange  its  particles, 
which  is  what  is  meant  by  the  term  "contract."     Contrac- 
tility does  not  mean  ability  to  occupy  less  space.     Distinc- 
tion must  be  made  between  "motion"  and  "locomotion"; 
when  an  amoeba  extends  a  pseudopod  and  then  withdraws 
it,  this  is  motion;  when  an  amoeba  changes  its  place,  or 
moves  on,"  this  is  not  only  motion,  but  also  locomotion. 

6.  It  breathes ;  the  energy  of  motion  is  maintained  by 
a  process  of  oxidation  going  on  within  the  substance  of 
the  amoeba.     Oxygen  is  absorbed  through  the  outer  surface 
and  unites  with  the  materials  of  the  body  of  the  amoeba. 
Its  energy  is  furnished  by  this  oxidation  as  truly  as  the 


Protozoa.  291 

energy  by  which   a  train  is  moved  is  furnished  by  the 
burning  (oxidation)  of  coal  in  the  engine. 

7.  It  produces  heat;   heat  is   another    form    of   energy 
which  always  results  from  oxidation.     We  are  always  pro- 
ducing some  heat,  even  when  we  are  as  quiet  as  possible, 
and  we  know  that  when  we  are  more  active  we  breathe 
faster  and  produce  more  heat.     So  with  the  amoeba.     But 
the  amoeba  should  be   classed  with   the   so-called    "  cold- 
blooded "  animals.     It  should  be  noted  that  not  only  do  all 
such  animals  have  a  rather  low  temperature,  but  it  is  a 
variable  temperature  and  usually  only  slightly  above  the 
temperature  of  the  surrounding  air  or  water.     The  amoeba 
is  constantly  producing  heat,  but  gives  it  off  to  the  water 
about  as  fast  as  it  is  made. 

8.  It  gives  off  waste  matter,  i.e.  it  excretes.     All  .oxidation 
produces  waste  matter.     Oxidation  of  wood  or  coal  pro- 
duces carbon   dioxid,  water,  and   ashes.     Our   breathing 
produces   carbon  dioxid,   water,  and   other  wastes  which 
we  throw  off  continually.     The  carbon  dioxid,  water,  and 
other  wastes  thrown  off  by  the  amoeba  are  small  in  amount, 
and,  being  invisible,  pass  out  into  the  water  unnoticed. 

9.  It  feels ;  when   a  foreign  body  comes   into   contact 
with  an  amoeba  it  usually  moves.     A  slight  electric  shock 
causes  it  to  assume  the   spherical  form.     There  is  good 
evidence  that  amoebae  have  the  sense  of  touch.     They  also 
seem  responsive  to  light  and  heat. 

10.  It  reproduces  its  kind ;  this  we  have  seen  is  done  in 
the  simplest  way  imaginable  ;  that  is,  merely  by  separating 
into  two  parts,  each  of  which  is  then  a  complete  individual. 
Multiplication  takes  place  by  division. 

Paramecium,  the  Slipper  Animalcule.  —  The  slipper  ani- 
malcule is  usually  to  be  found  in  the  water  collected  for 
amoebae.  In  aquariums  where  clams  have  been  kept, 


292 


Descriptive  Zoology. 


or  in  vases  where  flowers  have  been  standing  for  some 
time,  a  film  of  scum  is  likely  to  appear.  Just  underneath 
this  film  is  a  good  place  to  look.  Often  the  naked  eye 
may  detect  small  white  objects  moving  about.  These  are 
paramecia.  On  examining  some  of  the  water  with  a  low 
power  of  the  microscope,  one  discovers  that  these  tiny 
white  specks  are  oval  or  elliptical,  that  they  swim  actively, 


Course  of  food  vacuoles 


Contractile  vacuole 


Contractile  vacuole 


Ventral  view 


"","""111111111181111111111 

ANTERIOR       MACRO-     MICRO-      ^UTH      GULLET 
END  NUCLEUS    NUCLEUS 


SPOT 


CONTRACTILE 
VACUOLE 


POSTERIOR 
END 


Mouth      gullet  Food  ball 

FK5, 171.    PARAMECIUM,  THE  SLIPPER  ANIMALCULE. 

usually  with  the  same  end  foremost,  and  that  when  they 
run  against  an  obstruction  they  back  off  quickly.  They 
evidently  have  the  power  of  moving  and  the  sense  of 
touch.  Looked  at  with  a  higher  power,  the  shape  may  be 
determined  more  definitely.  They  are  somewhat  flattened, 
and  one  end  is  more  pointed  than  the  other.  The  dif- 
ference between  the  clear  ectoplasm  and  the  more 
granular  endoplasm  is  more  marked  than  in  the  amoeba. 


Protozoa.  293 

There  is  also  a  rather  distinct  layer,  or  cuticle,  forming 
the  outer  layer  of  the  ectoplasm.  The  whole  surface 
is  covered  with  small,  hairlike  projections  called  cilia. 
These  are  prolongations  of  the  protoplasm  which  makes 
the  body  of  the  paramecium.  These  have  the  power  of 
actively  lashing  back  and  forth,  acting  like  so  many  pad- 
dles, by  means  of  which  the  paramecium  swims.  At  the 
more  pointed  end,  usually  kept  in  the  rear,  there  is  a 
bunch  of  longer  cilia,  which  seem  to  serve  as  a  rudder. 
Sometimes  the  animal  reverses  its  direction  and  proceeds 
with  the  pointed  end  foremost,  but  ordinarily  only  for  a 
short  time,  to  back  out  of  a  tight  place  and  to  get  a  new 
start  in  another  direction. 

How  Paramecium  Eats.  —  Along  the  flat  surface  is  a 
groove,  which  at  one  end  forms  a  blind  passageway  dip- 
ping into  the  body.  Both  the  groove  and  the  tube,  which 
is  a  gullet,  are  lined  by  cilia.  By  their  vibrations  these 
cilia  collect  small  one-celled  plants  and  animals,  or  other 
particles  of  organic  matter,  which  accumulate  at  the  inner 
end  of  the  gullet.  From  time  to  time  -this  inner  end  is 
cut  off  by  constriction,  and  a  collection  of  food  particles, 
with  some  water,  is  pushed  into  the  soft  protoplasm  of 
the  body.  It  then  is  what  is  termed  a  food  ball,  or  some- 
times the  space  with  its  contents  is  designated  a  food 
vacuole.  These  food  vacuoles  may  be  regarded  as  so 
many  improvised  stomachs.  The  masses  slowly  rotate 
around  in  the  body  in  the  manner  indicated  by  the  arrows 
in  the  accompanying  figure.  At  a  point  about  opposite 
their  starting-point  any  undigested  residue  is  expelled 
through  a  weak  place  in  the  wall,  there  being  no  permanent 
anal  opening. 

Excretion  in  Paramecium.  —  There  are  usually  two  clear 
spaces  in  a  paramecium,  one  near  each  end.  These  may 


294  Descriptive  Zoology. 

be  seen  to  contract  at  tolerably  frequent  intervals,  appar- 
ently discharging  liquid  to  the  exterior.  Around  each  of 
these  "  contractile  vacuoles  "  is  a  series  of  radiating  canals. 
After  the  vacuole  has  become  obliterated  by  emptying  its 
contents,  it  is  gradually  filled  again  by  these  surrounding 
canals,  which  get  watery  material  from  the  various  parts 
of  the  body.  Thus  certain  waste  material  is  thrown  out. 

The  Nucleus.  —  Paramecium  has  two  nuclei,  a  larger 
body  called  the  macronucleus  and  a  smaller  called  the 
micronucleus. 

How  Paramecium  protects  Itself.  —  In  the  outer  part, 
or  cortex,  are  many  small  sacs,  each  containing  a  tiny 
thread.  When  a  paramecium  is  irritated,  it  discharges 
these  thread-cells,  which  appear  to  produce  a  stinging  or 
benumbing  effect  on  small  animals. 

Multiplication  of  Paramecia.  —  Like  the  amoeba  and 
the  vorticella,  the  paramecium  forms  new  individuals  by 
division.  The  constriction  is  transverse,  at  about  the 
middle,  and  finally  separates  the  one  into  two.  Both  the 
macronucleus  and  the  micronucleus  divide,  a  part  going 
with  each  half,  which  soon  after  separating  becomes  a 
complete  paramecium. 

VorticeJa,  the  Bell  Animalcule.  —  Another  interesting 
protozoan  is  Vorticella  or  the  bell  animalcule.  It  is 
found  on  submerged  stems  and  leaves  in  stagnant  water, 
sometimes  appearing  like  a  delicate  white  fringe.  Under 
a  low  power  of  the  microscope  a  vorticella  is  seen  to  be 
bell-shaped,  attached  by  a  slender,  flexible  stalk,  which 
joins  the  handle  end  of  the  bell-shaped  body  to  some  solid 
object.  When  the  animalcule  is  disturbed,  the  stalk  be- 
comes coiled,  jerking  the  body  up  close  to  its  support, 
where  it  is  much  more  secure  than  when  extended. 


Protozoa. 


295 


Examination  with  a  higher  power  shows  more  of  the 
structure  of  the  body.  The  bell-shaped  body  is  not  hol- 
low, but  is  made  up  of  protoplasm.  Across  the  mouth  of 
the  bell  is  a  disk,  which  is  slightly  narrower  than  the 
mouth  of  the  bell.  Between  the  disk  and  the  rim  of  the 
bell  is  a  circular  groove.  At  one  point  the  groove  dips 
down  into  the  body  of  the  bell,  forming  a  mouth  and  a 
gullet.  The  borders  of 'the  disk  and  the  bell  are  fringed 


Vestibule 
Cilia 

Gullet 

Contractile  vacuole 

Endoderm  ••' 
Ectoderm 


Disk 


Groove 


Macronucleus 

—  Micronucleus 


Stalk  ... 


Contractile  axis 


FIG.  172.      VORTICELLA,  THE  BELL  ANIMALCULE. 

with  cilia,  which  by  their  vibrations  create  water  currents 
and  thus  accumulate  food  material  in  the  inner  end  of 
the  gullet.  The  food  material  consists  largely  of  minute 
plants  and  animals  or  fragments  of  larger  forms.  As  in 
the  paramecium,  the  collection  of  food  particles  becomes 
pushed  farther  into  the  body,  becoming  a  food  ball,  or  food 
vacuole,  which,  with  others  preceding  and  following,  rotate 
around  the  body  in  regular  order.  At  the  outer  end  of 
the  gullet  is  a  space  called  the  vestibule.  Into  this  any 
undigested  residue  is  passed,  and  thus  swept  out  by  the 


296  Descriptive  Zoology. 

currents  maintained  by  the  cilia.  There  is  also  a  con- 
tractile vacuole,  which  is  near  the  vestibule  and  empties 
into  it.  The  vorticella  has  a  C-shaped  nucleus. 

How  Vorticella  protects  Itself. — When  a  vorticella  is 
disturbed  it  is  at  once  jerked  up  close  •  to  its  mooring 
by  the  coiling  of  its  stalk.  At  the  same  time  the  body 
changes  its  shape.  The  disk  is  drawn  in,  the  rim  of  the 
bell  turns  in,  the  cilia  are  inclosed,  and  the  body  becomes 
pear-shaped  or  even  spherical,  there  being  no  opening  left 
at  the  free  end.  After  the  disturbance  has  ceased,  the 
stalk  elongates,  the  bell  opens,  the  disk  protrudes,  the 
cilia  extend,  and  the  operations  of  active  life  are  all 
resumed. 

Development  of  Vorticella.  —  Vorticella  multiplies  by 
longitudinal  division.  For  some  time  two  bells  are  attached 
to  the  stalk,  but  one  finally  breaks  loose  and  swims  away 
by  means  of  its  cilia.  Later  it  becomes  attached  and 
develops  a  stalk. 

GENERAL  CHARACTERISTICS   OF    PROTOZOA. 

1.  The  protozoans  are  the  simplest  animals.     Most  of 
them  are  one-celled.     As  a  group,  they  are  the  smallest 
of  animals. 

2.  They  are  the  most  numerous,  in  individuals,  of  any 
branch  of  animals.     It  is  not  true,  as  commonly  believed, 
that  every  drop  of  water  swarms  with  animal  life.     One 
would  find   few  animalcules  in  ordinary  well   or  spring 
water.     But  they  usually  abound  in  stagnant  water.    There 
is    room    for  vast   numbers    of   these  lowly  forms  which 
occupy  so  little  space. 

3.  They  multiply  the  most  rapidly  of   all   animals.     In 
most  cases  multiplication  consists  simply  of  division  into 


Protozoa.  297 

two  equal  parts,  each  of  which  is  very  soon  a  complete 
individual,  ready  again  to  divide  in  the  same  manner. 
Their  great  number  is  due  to  their  rapid  multiplication, 
to  their  small  size,  which  makes  it  easy  for  them  to  find 
hiding  places,  and,  further,  to  their  complete  adaptation 
to  the  conditions  in  which  they  live.  Multiplication  does 
not  depend  wholly  on  division.  There  is  occasionally 
what  is  called  "conjugation";  that  is,  two  individuals 
come  together  and  more  or  less  completely  fuse.  At  any 
rate,  it  seems  to  be  proved  that  the  species  could  not  con- 
tinue to  live  indefinitely  without  the  occasional  occurrence 
of  conjugation.  And  this  is  supposed  to  be  true  of  most 
of  the  Protozoa. 

4.  They  are  the  oldest  of   animals ;    that  is,  they  are 
supposed  to  have  been  on  the  earth  longer  than  any  other 
kind   of   animals.      We    find    their  remains  in    very  early 
geologic  formations.     Some  of  them  are  supposed  to  have 
changed  but  little  as  time  passed,  the  conditions  of  their 
surroundings    being    comparatively    stable,    while    other 
groups  of  animals  have  been  greatly  modified  by  changes 
in  their  surroundings. 

5.  They  are  the  most  independent  of   animals.      The 
conditions  of  their  lives  are  such  that  they  could  live  with- 
out the  larger  animals,  while  many  of  the  latter  could  not 
live  without  them. 

Kinds  of  Protozoans.  —  There  are  many  kinds  of  pro- 
tozoans, some  of  them  widely  different  from  any  of  the 
three  forms  we  have  studied.  Some  are  parasitic.  One 
of  the  parasitic  forms  causes  malaria  when  introduced  into 
the  blood  by  the  proboscis  of  a  mosquito.  Some  proto- 
zoans, instead  of  having  cilia,  possess  a  few  longer  vibratile 
projections  called  flagella.  In  the  one-celled  forms  there 
is  usually  one  flagellum,  or,  at  most,  two.  But  the  colonial 


298  Descriptive  Zoology. 

protozoans  are  composed  of  several  or  many  cells,  each  of 
which  may  have  a  pair  of  flagella.  Thus  there  are  three 
principal  modes  of  locomotion  among  protozoans  :  (i)  slow 
creeping  by  means  of  pseudopods,  as  in  amoeba;  (2)  swim- 
ming by  cilia,  as  in  paramecium  ;  (3)  more  active  swimming 
by  flagella,  this  mode  being  not  very  unlike  the  second. 

The  Shell-bearing  Protozoans.  —  Many  protozoans  have 
shells.  Some  of  these  shells  are  composed  of  lime,  others 
of  silica,  while  still  others  are  formed  of  grains  of  sand 
which  the  protozoan  glues  together  by  a  secretion  from  its 
protoplasm.  Most  of  these  shelled  forms  live  in  the  ocean. 
Some  of  the  shells  are  borne  where  we  should  expect  them, 

on  the  outside,  the  animal  being 
able  to  withdraw  into  the  shell 
and  project  again  at  will  through 
an  opening.  But  in  many  the  ani- 
mal cannot  thus  withdraw  itself 
completely  into  the  shell.  Many 

of  the  shells  are  perforated  by  nu- 
FIG.  173.    NOCTILUCA. 

merous  minute  openings,  through 

A  phosphorescent  marine  protozoan. 

which  fine  threads  of  protoplasm 

are  extended,  these  projecting  threads  sometimes  forming 
a  network  outside  of  the  shell.  In  many  forms  the  proto- 
plasm increases  in  amount,  flows  out  of  the  main  opening 
of  the  shell,  and  forms  a  new  shell,  larger  than  the  old  one, 
but  attached  to  it.  In  this  way  it  proceeds,  making  a  series 
spirally  arranged,  similar  in  general  appearance  to  a  spirally 
coiled  snail  shell,  or  the  chambered  nautilus. 

Chalk.  —  One  of  the  most  abundant  and  best  known  of 
geologic  formations  is  made  by  protozoans.  Chalk  is 
made  up  of  the  shells,  such  as  above  described,  of  a  kind 
of  protozoan  known  as  Globigerina.  Myriads  of  these 
protozoans  live  in  the  ocean.  When  they  die,  their  skele- 


Protozoa.  299 

tons  slowly  settle  to  the  bottom.  Dredgings  from  the 
bottom  of  the  Atlantic  Ocean  contain  a  gray  mud  which, 
under  the  microscope,  is  found  to  be  largely  composed  of 
these  shells.  So  where  we  find  chalk  rock  on  land,  we 
know  that  region  was  once  the  bed  of  the  ocean.  This 
once  soft  mud  has  become  hardened,  by  drying  or  by 
pressure,  sometimes  by  both,  into  hard  rock,  a  variety  of 
limestone  known  as  chalk.  A  generation  ago  the  car- 


FIG.  174.    A  SHELL-BEARING  PROTOZOAN  (GLOBIGERINA). 

From  Packard. 

penter  and  the  schoolboy  used  a  rough  broken  lump  of 
the  chalk  rock.  The  ordinary  school  crayon,  however, 
usually  contains  no  chalk.  Any  one  who  has  used  the 
old  lump  chalk  will  recall  that  occasionally  he  struck  a 
hard,  flinty  place,  due  to  the  mixture  of  other  material. 

Silicious  Earth.  —  Other  kinds  of  protozoans  form  their 
shells  of  silica.  Beds  of  this  material  are  found  in  various 
parts  of  the  world  and  are  used  as  polishing  material, 
under  the  names  Tripoli,  Barbadoes  earth,  etc.  Many  of 
the  shells  of  silica  are  exceedingly  beautiful  in  form. 


joo  Descriptive  Zoology. 

Distribution  of  Protozoa.  —  All  protozoans  are  aquatic, 
though  some  might  seem  to  be  exceptions,  living  as  they 
do  in  damp  moss ;  but  they  are  probably  in  thin  films  of 
water  on  the  surface.  Protozoans  are  the  most  widely 
distributed  of  animals,  occurring  almost  all  over  the  globe, 
in  fresh  water  and  in  the  ocean,  in  lakes  and  rivers,  ponds 
and  creeks,  pools  and  ditches.  In  the  ocean  they  are 
more  abundant  in  shallow  water,  but  are  also  found  at 
considerable  depths  and  at  the  surface  of  the  deeper  seas. 

The  Importance  of  Protozoa.  —  Protozoans  are  highly 
important  in  two  respects:  (i)  they  have  contributed 
much  to  rock-making,  and  are  still  making  deposits  on  the 
ocean  bottom ;  (2)  as  a  source  of  food  to  the  animals  of 
the  ocean,  it  is  difficult  to  overestimate  their  importance. 
In  countless  myriads  they  serve  as  food  for  animals  some- 
what larger  and  higher  in  the  scale  than  themselves. 
These  animals,  in  turn,  are  the  food  for  still  higher  animals. 
The  protozoans,  then  (with  the  protophytes  or  one-celled 
plants),  may  truly  be  said  to  be  the  food  foundation  of  all 
the  higher  marine  animals. 

PROTOZOA  AND   METAZOA. 

Protoplasm.  —  Protoplasm  is  the  living  substance  of 
animals  and  plants.  It  is  a  clear,  jellylike  substance, 
which  does  not  dissolve  in  water  nor  readily  mix  with  it. 
When  seen  in  water  its  outlines  are  usually  quite  distinct. 
It  may  appear  more  or  less  dotted  on  account  of  various 
kinds  of  matter  suspended  in  it.  An  amoeba  is  a  mass 
of  protoplasm,  and  the  properties  of  protoplasm  were  con- 
sidered in  connection  with  amoeba.  Protoplasm  has  the 
power  of  movement,  is  capable  of  being  stimulated,  i.e.  is 
irritable,  it  eats,  grows,  breathes,  throws  off  waste  matter, 
or  excretes,  and  has  the  power  of  reproduction. 


Protozoa.  301 

Protoplasm  is  killed  by  very  high  temperature,  killed  or 
its  activity  checked  by  low  temperature,  and,  in  general, 
requires  the  conditions  that  we  usually  recognize  as  neces- 
sary for  life. 

In  its  chemical  composition  protoplasm  is  exceedingly 
complex.  Protoplasm  is  a  living  substance,  and  any 
attempt  to  analyze  it  kills  it;  hence  its  exact  composition 
cannot  be  known.  But  the  dead  material  left  when  it  has 
been  killed  can  be  analyzed,  and  consists  largely  of  a  sub- 
stance called  proteid.  This  consists  of  carbon,  hydrogen, 
oxygen,  and  nitrogen,  with  some  sulphur,  traces  of  iron, 
and  compounds  of  phosphorus,  potassium,  calcium,  and 
magnesium.  Protoplasm  seems  to  be  a  very  unstable 
compound,  as  we  should  naturally  expect  from  its  com- 
plexity. Then,  too,  in  its  life  and  growth,  it  is  constantly 
changing,  and,  undoubtedly,  changes  more  or  less  in  its 
composition  from  time  to  time. 

The  Cell.  —  Sometimes  protoplasm  occurs  in  a  consider- 
able mass,  without  any  separation  into  distinct  parts.  But 
usually  it  is  found  in  more  or  less  distinct  particles,  .and 
these  distinct  particles  of  protoplasm  are  called  "  cells." 
There  may  be  a  cell  wall  distinct  from  the  mass  of  proto- 
plasm, but  this  is  not  essential  to  a  cell.  Within  the  cell  is 
a  more  dense  appearing  portion  called  the  "nucleus."  A 
cell  living  independently  tends  to  be  spherical,  though  since 
it  has  the  power  of  changing  its  shape,  it  often  departs 
from  the  typical  form.  When  an  amoeba  goes  into  the 
resting  stage  it  assumes  the  spherical  form. 

Protozoa  and  Metazoa.  —  The  protozoans  are  typically 
one-celled  animals.  The  other  animals  are  many-celled 
and  are  called  metazoans.  Their  greater  size  is  not  due 
to  their  having  larger  cells,  but  to  the  increased  number 
of  cells. 


302  Descriptive  Zoology. 

Development  of  Metazoa.  —  Every  metazoan  begins  life 
as  a  single  cell  (except  in  multiplication  by  budding).  It 
starts  as  an  egg  (ovum  or  egg  cell),  having  very  much 
the  same  characteristics  as  an  'amoeba.  After  being  fer- 
tilized it  soon  divides  into  two  parts,  but  these  halves, 
instead  of  separating,  as  in  the  case  of  the  amoeba,  re- 
main together.  These  halves  divide  into  quarters,  and 
so  on,  into  8,  16,  32,  64,  128,  etc.,  parts,  until  they  become 
too  numerous  to  be  counted.  After  a  time  these  numer- 
ous cells,  still  remaining  together,  arrange  themselves  in 
the  shape  of  the  animal  that  produced  the  egg  cell. 

Division  of  Labor  in  Communities.  —  A  solitary  back- 
woodsman has  to  do  everything  for  himself.  He  gets  and 
prepares  his  own  food,  provides  needed  shelter,  makes  his 
own  clothing.  But  if  he  has  a  partner,  there  is  sure  to  be 
some  division  of  their  labor.  One  can  do  some  things 
better  than  the  other,  and  they  find  that  it  is  advantageous 
for  each  to  do  what  he  can  do  best.  In  an  Indian  family 
the  men  do  the  hunting  and  fighting,  while  the  squaws  pre- 
pare the  food,  dress  the  hides  for  clothing  and  lodges,  etc. 
It  is  hardly  necessary  to  call  attention  to  the  saving,  of  time 
that  results  from  such  a  division  of  labor,  or  to  note  the  finer 
quality  and  finish  of  the  various  articles  of  common  use 
when  they  are  made  by  one  who  acquires  skill  by  the  con- 
stant practice  which  comes  from  devoting  himself  entirely  to 
one  kind  of  work.  It  is  evident  that  no  one  man  can  do  many 
things  and  do  them  all  as  well  as  when  the  work  is  divided. 

Physiological  Division  of  Labor.  —  An  amoeba  does  every- 
thing for  itself.  Of  course  it  lives. very  well  in  its  simple 
way,  and  is  well  adapted  to  its  mode  and  place  of  life. 
But  it  does  too  many  things  to  do  any  of  them  very  well. 
It  can  move  but  slowly,  it  is  dull  of  sensation,  etc.  Sup- 
pose that,  when  an  amoeba  divides,  the  two  parts  remain 


Protozoa.  303 

adhering  to  each  other,  and  that  it  divides  again,  making 
four  parts,  and  each  of  these  divides,  making  eight  parts 
remaining  in  one  mass.  It  is  easy  to  see  how  one  might 
attend  to  the  moving,  another  to  the  work  of  feeling,  a 
third  to  eating  and  digesting,  a  fourth  to  breathing,  a  fifth 
to  the  work  of  dividing  for  the  spread  of  the  species,  while 
the  other  three  became  more  or  less  flattened  and  spread 
out  over  the  others  to  protect  them.  This  will  serve  to 
give  an  idea  of  what  actually  takes  place  when  the  egg 
cell  of  a  metazoan  has,  by  division,  become  a  many-celled 
mass.  Each  cell  has  primarily  all  the  characteristics 
common  to  an  amoeba,  —  that  is,  they  all  have  power  to 
move,  eat,  digest,  feel,  breathe,  divide.  But  such  a  large 
mass  would  be  unwieldy  unless  it  had  some  support ; 
hence  some  cells  may,  to  the  advantage  of  the  whole, 
become  harder  and  stronger  to  hold  the  soft  cells  in  place. 
In  this  now  heavier  mass  there  is  more  danger  of  mechani- 
cal injury  to  the  outside,  and  the  outside  layer  by  harden- 
ing will  serve  to  protect  the  inner,  more  delicate  cells  from 
harm.  If  the  outside  cells  harden,  the  animal  will  no 
longer  be  able  so  well  to  absorb  oxygen  for  the  interior 
cells,  nor  can  it  now  take  in  food  at  any  point.  Special 
arrangement  must  be  made  to  take  oxygen  and  food  into 
the  interior,  where  soft  cells  can  do  the  work  of  preparing 
it  for  use  in  the  body.  These  inner  cells  have  now  more 
work  than  before,  for  they  must  prepare  the  material  for 
building  and  maintaining  the  cells  that  have  given  up  their 
power  of  digesting  that  they  might  fit  themselves  for  pro- 
tection. In  proportion  as  any  given  cell  devotes  itself  to 
one  kind  of  work,  it  must  lose  more  or  less  the  ability  to  do 
the  other  kinds  of  work  that  it  primarily  could  do.  This 
is  what  is  meant  by  physiological  division  of  labor.  All 
the  cells  resulting  from  the  division  of  a  metazoan  egg 


304  Descriptive  Zoology. 

cell  are  at  first  essentially  alike  in  structure  and  function. 
To  fit  themselves  for  the  different  kinds  of  work  that  they 
have  to  do,  they  grow  different.  This  growing  different 
is  called  differentiation.  Each  becomes  fitted  for  one 
special  work  ;  this  is  specialization. 

Tissues.  —  In  the  higher  metazoans  there  are  many 
cells  devoted  to  each  of  the  different  kinds  of  work  to  be 
done.  This  we  should  naturally  expect,  for  in  such  a 
body  there  are  myriads  of  cells,  but  only  comparatively 
few  kinds  of  work.  As  has  already  been  made  clear,  an 
amoeba  can  do  nearly  all  the  kinds  of  work  that  any 
animal  can  do,  though  in  a  much  simpler  way.  The  func- 
tions of  animals  are  summed  up  in  saying  they  move,  feel, 
eat,  grow,  breathe,  protect  themselves,  and  reproduce  their 
kind.  Stated  more  formally,  the  functions  of  animals  are 
included  in  the  processes  of  motion,  sensation,  support,  pro- 
tection, reproduction,  and  nuttition  (nutrition  including 
digestion,  absorption,  circulation,  respiration,  and  excretion). 

For  instance,  muscle  cells  are  cells  devoted  to  the  work 
of  motion  ;  they  have  largely  given  up  the  other  functions 
that  they  originally  possessed.  The  nerves  have  lost  the 
ability  to  change  their  form,  in  devoting  themselves  to 
the  special  work  of  sensation.  So,  too,  with  the  cells 
of  the  supporting  and  protective  tissues. 

A  tissue  is  a  group  of  cells  having  the  same  structure 
and  function. 

An  amoeba  consists  of  a  single  cell,  but  it  can  do  a 
number  of  kinds  of  work.  A  tissue  consists  of  many  cells, 
but  they  all  do  the  same  kind  of  work.  In  other  words, 
an  amoeba  is  simple  in  structure,  but  complex  in  function ; 
a  tissue  is  complex  in  structure,  but  simple  in  function. 

Organs.  —  In  addition  to  the  differentiation  of  cells  into 
tissues,  there  is  a  still  further  division  of  labor  by  having 


Protozoa.  305 

certain  distinct  parts  of  the  body  devoted  to  a  special 
work ;  for  instance,  the  hand  is  adapted  to  the  work  of 
grasping ;  it  is  an  organ  and  its  special  work,  or  function, 
is  prehension.  But  the  hand  is  composed  of  several  kinds 
of  tissues.  It  is  supported  by  bony  tissue,  the  muscular 
tissue  gives  motion  to  the  fingers,  the  nerves  are  composed 
of  nervous  tissue,  connective  tissue  makes  up  the  tendons 
and  part  of  the  muscle,  and  the  skin  is  another  kind  of 
tissue.  In  addition  there  is  usually  some  fat,  which  is 
considered  a  still  different  tissue.  The  higher  animals  are 
organisms,  —  that  is,  they  are  made  up  of  organs,  each  of 
which  has  its  special  function  to  perform.  In  other  words, 
each  organ  works  for  every  other  organ  in  the  organism, 
and  every  other  organ  works  for  it. 

The  Colonial  Protozoa.  —  This  name  is  given  to  the 
protozoans  that  have  more  than  one  cell,  some  of  them 
being  actually  many-celled.  The  simplest  of  these  proto- 
zoans are  little  more  than  an  aggregation  of  cells,  each  of 
which  leads  a  nearly  independent  life,  doing  its  own  diges- 
tion, etc.  There  is  almost  no  division  of  labor  among 
them.  Others  form  a  true  colony,  and  there  is  a  rather 
gradual  series  in  development  until  in  the  higher  forms 
there  is  a  division  of  labor  approaching  that  found  in  the 
simpler  Metazoa.  The  cells  in  the  simpler  colonial  proto- 
zoans lead  lives  so  nearly  independent  of  their  associates 
that  we  might  imagine  the  colony  falling  to  pieces  and 
each  cell  again  taking  up  an  independent  life,  like  that 
of  the  amoeba.  Not  so,  however,  with  the  metazoans. 
After  their  differentiation  in  structure  and  specialization 
in  function  they  are  so  modified  that  they  could  no  longer 
live  independently.  In  developing  one  function  each  cell 
has  neglected  other  functions  till  now  it  is  no  longer  able 
to  perform  them.  In  other  words,  it  has  become  dependent. 


306  Descriptive  Zoology. 

Each  cell  lives  and  works,  not  merely  for  itself,  but  for 
all.  In  their  cooperation  these  units  of  a  lower  order  have 
become  so  united  as  to  form  "  a  unit  of  a  higher  order,"  as 
the  mathematician  expresses  it. 

The  cell  is  the  unit  of  structure  in  animals,  and  where 
the  cells  unite  and  specialize  they  form  a  many-celled  in- 
dividual, in  the  strict  sense  of  the  word,  —  that  is,  it  can- 
not now  be  divided  without  destroying  the  life  of  the  whole 
complex  individual. 

There  is  one  exception :  the  egg  cells  can,  and  do,  live 
separately.  This  is  their  work,  to  separate  from  the  body 
as  a  whole,  for  the  express  purpose  of  growing  into  new 
individuals. 


CHAPTER  XIX. 


BRANCH    PORIFERA. 

THE   SPONGES. 

The  Simplest  Sponge.  —  The  simplest  sponge  is  a  vase- 
shaped  body  attached  by  the  base.  It  is  hollow,  and  has 
an  opening  (osculum)  at  the  free  end.  Through  the  wall 
are  many  small  holes,  and  water  is  constantly  entering 
these  holes  (inhalant  pores)  and  passing  out  of  the 
mouth  of  the  vase.  The  cause  of 
this  current  is  the  vibration  of  many 
flagella,  which  project  inward  from 
the  cells  lining  the  cavity.  This 
current  of  water  brings  oxygen  and 
food,  consisting  of  minute  plants 
and  animals,  and  remains  of  larger 
animals  and  plants.  The  vaselike 
body  is  supported  by  a  large  number 
of  three-rayed  spicules,  embedded 
in  the  wall  of  the  vase.  These  are 
composed  of  carbonate  of  lime,  and 
they  constitute  the  skeleton,  making 
the  body  fairly  firm,  and  yet  leaving 
it  flexible  and  elastic.  An  outer  layer  of  cells  constitutes 
the  ectoderm,  the  lining  cells  are  the  endoderm,  while 
between  these  is  a  thin  layer  called  the  mesoderm,  in 
which  the  spicules  are  embedded.  (See  Fig.  176.) 

More  Complex  Sponge.  —  Somewhat  higher  is  a  sponge 
that   is   vase-shaped,   or  cylindric,  in  which  the   inhalant 

307 


FIG.  175.     SIMPLE  SPONGE, 
MARINE. 

Water  enters  minute  holes  in  the 
sides  and  passes  out  of  the 
opening  at  the  top  of  the  tube. 


308 


Descriptive  Zoology. 


pores  do  not  lead  directly  into  the  main  cavity  (as  shown  in 
Figs.  176  and  177),  but  do  so  indirectly.  The  cells  bearing 
the  flagella,  instead  of  lining  the  main  cavity,  are  here  in 
the  radiating  canals  that  open  into  the  main  cavity,  and 

receive  the  water  through  cross 
openings  from  the  incurrent 
canals.  As  in  the  simpler 
sponge,  there  are  supporting 
spicules  in  the  walls. 

The  Highest  Sponges. —  The 
general  plan  of  structure  of  the 
highest  sponges  may  be  illus- 
trated by  Fig.  178.  The  most 
noticeable  peculiarities  are  two  : 
( i )  The  cilia  are  limited  to  cer- 
tain cavities,  or  enlargements, 
along  the  course  of  the  passages 
from  the  outside  to  the  main 
cavity.  These  cavities  are  called 
the  "ciliated  chambers."  (2) The 
whole  sponge  is  no  longer  a 
vase  or  cylinder,  but  a  mass,  in 
which  the  cavities  are  less  con- 
spicuous. This  is  due  to  the 
increase  of  the  middle  layer,  or 

ONE  OF  THE^LEST  SPONGES,    ™esoderm,  a  gelatinous  mass  of 
Caicoiynthus  primigenius.          cells.    As  before,  the  outer  layer 
(After  Haeckei.)  is  the  ectoderm,  and  the  lining 

the  endoderm. 

Kinds  of  Skeletons. —  Sponges 
may  be  classed,  according  to  the  nature  of  their  skeletons, 
into  three  groups  :  — 

i.    Calcareous    sponges,    whose    skeletons     consist    of 


A  part  of  the  outer  wall  is  cut  away  to 
show  the  inside.  —  From  Jordan  and 
Kellogg's  Animal  Life. 


Porifera. 


309 


spicules  of  carbonate  of  lime,  as  seen  in  the  simple  sponge 
described.  These  spicules  have  various  forms,  but  the 
three-rayed  form  is  most  common.  They  often  resemble 
crystals. 

2.  The    silicious    sponges,    with    spicules   of    silica   or 
flint.     These  skeletons  often  appear  to  be  made  of  spun 
glass,  and  many  of  them  are 

of  great  beauty,  one  of  the 
most  noted  being  the  Venus's 
flower  basket,  found  about 
the  Philippine  Islands. 

3.  The  horny  sponges,  or 
sponges  of  commerce.    These 
skeletons    are    composed    of 
a   substance   called    spongin, 
whose   chemical  composition 
resembles   that   of  silk.     Its 
fine,  threadlike  fibers  branch 
and    interweave,    forming   a 
feltlike  structure,  with  which 

all  are  familiar.  Its  chief  value  consists  in  its  absorbing 
power,  and  this,  in  turn,  depends  on  its  softness,  fineness, 
and  elasticity.  Its  durability  is  also  a  factor  in  its  value. 
Some  sponges  have  both  silicious  spicules  and  horny  fibers. 
The  Commercial  Sponge  at  Home.  — If  one  could  "call 
upon  "  one  of  these  sponges,  he  would  find  it  attached  to 
rock  at  the  bottom  of  a  warm  sea.  He  would  see  a  round- 
ish mass  with  a  smooth  exterior,  in  color  and  finish  not 
unlike  a  dark-colored  kid  glove.  He  might  see  several 
large  openings,  from  which  currents  of  water  are  emerg- 
ing, bearing  carbon  dioxid  and  other  impurities.  Over  the 
surface  he  might  discover  smaller  holes,  into  which  the 
water  flows,  bearing  oxygen  and  food.  If  he  were  to  dis- 


FIG.  177.   CROSS  SECTION  OF  SIMPLE 
TUBULAR  SPONGE. 

Showing  Ci)  three-pointed  spicules  (skele- 
ton) ,  (2)  cilia  which  bring  in  water  through 
(3)  the  holes  in  the  sides  of  the  tube. 


3io 


Descriptive  Zoology. 


turb  the  sponge,  these  smaller  openings  would  close,  and 
perhaps  the  larger  ones  also.  If  he  now  tried  to  pick  it 
up,  it  would  be  found  firmly  attached.  Effort  to  detach 
it  by  pulling  would  probably  crush  it,  and  show  that  the 
whole  has  about  the  consistency  of  beef  liver.  It  is  easy 
to  squeeze  out  all  of  the  soft  tissue  and  leave  the  elastic 
skeleton. 

Source  of  Commercial  Sponges. — The  most  valuable  of  the 
sponges  of  commerce  come  from  the  Mediterranean  ;  many 
also  come  from  the  Red  Sea,  Florida,  and  the  West  Indies. 


Water 
Exit 


FIG.  178.    DIAGRAM  OF  A  COMMERCIAL  SPONGE. 

Collecting  Sponges.  —  Sponges  are  collected  by  divers,  or 
by  the  use  of  rakes,  or  by  dragging  hooks.  They  are  piled 
on  shore  to  allow  the  soft  tissues  to  decay,  after  which 
they  are  washed,  dried,  sorted,  trimmed,  and  shipped  to 
market.  The  finer  ones  are  usually  bleached.  Sometimes, 
in  trimming  away  the  base  where  they  are  attached  to 
the  rock,  enough  is  cut  away  to  leave  a  large  hole ;  this 
is  the  lower  end  of  the  cloaca,  or  main  cavity. 

Fresh-water  Sponges.  —  Most  of  the  sponges  are  marine, 
but  there  is  one  family  of  sponges  in  fresh  water.  It  is 
not  uncommon  to  find  them  in  lakes  and  rivers,  where  they 


Porifera.  311 

form  a  coating  on  logs  and  rocks,  usually  greenish  or 
yellowish  green.  In  still  water  they  branch  and  may 
reach  considerable  height,  but  in  swift  streams  form  a  low, 
spreading  mat.  They  are  of  no  commercial  value.  Some- 
times in  reservoirs  supplying  drinking  water  they  give  an 
unpleasant  taste  to  the  water. 

Relations  of  Sponges  to  Other  Animals.  —  None  of  the 
larger  animals  eat  sponges.  This  may  be  due  to  the  pres- 
ence of  the  sharp  spicules,  or  to  an  unpleasant  taste  or 
odor.  Many  small  animals  bore  into  or  crawl  into  them, 
some  for  a  safe  hiding  place,  doing  no  direct  injury  to 
their  host.  Others  are  perhaps  parasitic.  While  no 
sponge  is  a  parasite,  some  injure  shells,  as  oysters,  by  bor- 
ing into  them.  Certain  sponges  are  found  only  on  the 
shells  inhabited  by  hermit  crabs,  where  they  pay  for  their 
transportation  by  concealing  their  bearer. 

Reproduction  and  Development  of  Sponges.  —  Sponges 
have  two  ways  of  multiplying,  —  by  budding  and  by  eggs. 

In  budding,  a  group  of  cells,  called  a  "  gemmule,"  is 
formed,  which  becomes  detached,  and  develops  into  a 
sponge.  Fresh-water  sponges  form  these  gemmules  in  the 
fall.  The  gemmules  lie  dormant  over  winter,  and  begin 
growth  in  the  spring. 

Sponges  produce  eggs.  These  eggs  are  cells,  which  are 
produced  by  the  middle  layer  of  the  sponge  (mesoderm). 
Other  cells,  called  sperm  cells  (or  sperms),  are  produced 
by  some  other  part  of  the  mesoderm,  or  perhaps  by  the 
mesoderm  of  another  sponge.  After  the  egg  cell  is  ferti- 
lized by  the  sperm  cell,  it  begins  to  divide,  and  forms  a 
number  of  cells  which  cohere.  Part  of  these  cells  have 
cilia,  and  by  their  vibration  the  embryo  sponge  swims 
about,  until  finally  it  settles,  attaches  itself,  and  remains 
fixed  the  rest  of  its  life.  While  it  is  small  and  free,  the 


312  Descriptive  Zoology. 

vibration  of  cilia  propels  it  through  the  water;  after  it 
becomes  attached,  the  vibration  of  cilia  creates  water 
currents,  which  bring  it  food  and  oxygen. 

Rank  of  Sponges. — The  sponges  are  many-celled  and 
evidently  higher  than  the  colonial  protozoans.  But  there 
is  no  high  degree  of  differentiation  of  parts.  The  cells 
bearing  flagella  and  the  egg  and  sperm  cells  are  differ- 
ent from  the  others.  But  there  are  no  special  distinct 
organs  for  the  performance  of  special  functions.  In  com- 
paring them  with  other  forms,  it  may  be  seen  that  they 
are  plainly  the  lowest  of  the  metazoa. 


CHAPTER   XX. 


BRANCH   CCELENTERATA. 

[This  branch  includes  the  Hydroids,  Jellyfishes,  Sea  Anemones, 
and  Coral  Polyps.] 

Example.  —  The  Fresh-water  Polyp,  Hydra. 

Naked-eye  Appearance  of  Hydra.  —  In  examining  a  jar 
of  aquatic  plants  one  may  find  attached  to  them  slender 
cylindric  bodies  about  half  an  inch  long  and  of  the  thick- 
ness of  a  needle.  Extending  from  the  free  end  are  several 
fine,  threadlike  tentacles,  which  may  be  as  long  as  the 
body  itself.  Hydras  are  often  white  or  colorless,  but  occa- 
sionally brown  or  green  ones  are  found.  If  undisturbed, 
the  body  and  tentacles  may  occa- 
sionally sway  gently  to  and  fro. 
If  disturbed,  a  hydra  usually 
shortens  until  it  is  a  tiny  ball. 
The  tentacles  also  shorten  until 
they  look  like  a  circle  of  tiny  buds. 

Structure  Of  Hydra.  -Micro- 
scopic  examination  is  required  to 
learn  much  of  the  structure  of  hydra.  The  cylindric  body 
is  hollow,  and  the  hollow  extends  through  the  tentacles, 
which  are  closed  at  their  tips.  Above  the  circle  of 
tentacles  rises  a  cone-shaped  body  called  the  hypostome, 
at  the  apex  of  which  is  the  mouth.  The  body  wall  consists 
of  two  layers,  the  outer  being  the  ectoderm,  and  the  inner 
the  endoderm.  Between  these  two  is  a  layer  called  the 
mesoglcea. 

313 


HYDRA  EXTENDED. 


Descriptive  Zoology. 


The  Ectoderm.  — The  cells  of  the  ectoderm  are  clear,  and 
more  uniform  in  size  than  those  of  the  endoderm.  At 
their  inner  ends  they  are  narrower,  and  usually  end  in 
slender  prolongations,  which  bend  at  a  right  angle  to  the 
main  axis  of  the  cell,  and  help  make  a  sort  of  middle  layer 
between  the  endoderm  and  ectoderm.  These  prolonga- 


Tentacle . 


Spermary 


Bud 


Cross  section 


FIG.  180.    HYDRA,  LONGITUDINAL  SECTION. 

tions  are  called  muscle  processes  and  are  the  chief  agents 
in  shortening  and  moving  the  body.  Between  the  nar- 
rowed bases  of  the  larger  ectoderm  cells  are  smaller  cells, 
which  are  supposed  to  be  sensitive,  and  may  perhaps  be 
properly  called  nerve  cells. 

Stinging  Cells.  —  Among  the  cells  of  the  ectoderm,  both 
of  the  body  and  of  the  tentacles,  are  peculiar  bodies  called 


Coelenterata. 


315 


thread  capsules,  stinging  cells,  or  nematocysts.  These 
are  elliptical,  and  before  being  disturbed  have  a  fine 
thread  coiled  within.  When  the  hydra  is  irritated,  the 
nematocysts  are  discharged  and  the  threads  are  suddenly 
darted  out.  At  the  base  of  each  thread,  close  to  the 
capsule,  are  a  few  fine  barbs,  and  it  is  supposed  that  a 


Cell  containing 
thread  capsule 


Thread  capsule 
partly  discharged 

FIG.  181.    STINGING  CELLS  OF  HYDRA,  HIGHLY  MAGNIFIED. 


Thread  capsule 
fully  discharged 


poisonous  substance  is  contained  within  the  capsule.  At 
any  rate,  the  result  of  coming  in  contact  with  this  sort 
of  apparatus  is  a  stinging  sensation,  like  that  caused  by 
nettles,  but,  of  course,  the  hydra  is  so  small  that  it  does 
not  produce  much  effect  except  on  very  small  animals. 
But  let  a  small  crustacean,  such  as  a  water  flea,  swim 
against  a  hydra's  tentacle,  and  it  is  usually  paralyzed  at 
once.  Then  the  tentacles  draw  the  victim  to  the  mouth 
and  it  is  swallowed. 


Descriptive  Zoology. 

The  Endoderm.  —  The  cells  of  the  endoderm  are  larger 
than  those  of  the  ectoderm.  They  are  also  less  uniform 
in  size.  They  are  darker  colored,  sometimes  containing 
brown  coloring  matter.  The  green  hydra  contains  chloro- 
phyll. The  endoderm  cells  often  exhibit  amoeboid  move- 
ments, and  frequently  show  food  particles  and  large 
contractile  vacuoles,  such  as  noticed  in  amoeba.  Project- 
ing from  these  cells  into  the  cavity  are  sometimes  found 
large  flagella. 

Digestion  in  Hydra.  —  When  food  is  taken  into  the  central 
cavity  it  is  supposed  to  be  partly  digested  here,  this  often 
being  called  the  digestive  cavity.  But,  at  any  rate,  parti- 
cles not  completely  digested  are  taken  into  the  endoderm 
cells,  where  no  doubt  digestion  takes  place ;  and  from  the 
material  digested  by  the  endoderm  cells  the  ectoderm  gets 
its  nourishment.  We  here  see  a  division  of  labor,  the  outer 
layer  producing  the  motion,  obtaining  the  food,  and  pro- 
tecting the  whole,  while  the  inner  cells  do  the  work  of 
digestion. 

Locomotion.  —  While  the  hydra  is  pretty  firmly  attached 
by  means  of  a  sticky  substance  secreted  by  the  cells  of  the 
base,  it  can  let  go  and  move  away.  It  sometimes  bends 
over,  attaches  itself  by  the  tentacles,  and  then  lets  go  at 
the  base  and  pulls  the  base  up  close  to  the  place  where  the 
tentacles  are  fastened,  and  by  repeating  this  action  crawls 
along  like  a  "measuring  worm."  Or  it  may  bend  over, 
attach  itself  by  the  tentacles,  let  go  at  the  base,  and  turn 
the  base  clear  over,  thus  turning  a  complete  somersault, 
though  slowly,  instead  of  with  a  spring.  Sometimes,  also,  it 
appears  to  crawl  slowly  by  means  of  the  tentacles  alone. 
But  hydra  is  not  a  great  traveler,  preferring  to  wait  for 
something  to  turn  up,  rather  than  hunt  for  food.  We  see 
how  well  fitted  it  is  for  a  sedentary  life,  for  with  the  long, 


Coelenterata.  317 

outstretched  tentacles,  with  their  many  stinging  cells,  it 
has  a  trap  continually  set  for  the  unwary  small  swimmers 
that  abound  in  such  places  as  the  hydra  inhabits. 

Recovery  after  Mutilation.  —  One  very  remarkable  fact 
about  hydra  is  its  ability  to  live  and  grow  after  injury.  If 
cut  into  several  pieces,  each  grows  into  a  complete  hydra. 

Multiplication  by  Budding.  —  Hydra  multiplies  by  bud- 
ding. A  small  part  of  the  wall  bulges  out  and  forms  a 
cylindric  branch,  with  a  double  wall  continued  from  the 
two  layers  of  the  body,  and  the  hollow  of  the  branch  is 
continuous  with  that  of  the  body  (see  Figs.  179  and  180). 
After  a  while,  a  circle  of  tentacles  is  formed  at  the  end  of 
the  branch,  and  an  opening  appears  at  the  end  for  a  mouth. 
Finally  the  base  of  the  branch  is  constricted  and  the  branch 
separates  and  is  an  independent  hydra. 

Multiplication  by  Eggs.  —  Among  the  cells  of  the  ecto- 
derm, we  noticed  that  certain  cells  are  smaller  and  lie 
deeper  than  the  others.  Some  of  these  cells  develop  into 
egg  cells,  or  eggs.  They  are  covered  by  the  outer  cells, 
but  make  a  marked  bulging.  This  is  the  ovary  (from  ova, 
eggs)  and  is  usually  found  at  about  one  third  of  the  length 
from  the  foot  of  the  hydra  (see  Fig.  180).  A  somewhat 
similar  growth  occurs  near  the  tentacles,  but  the  contained 
cells  are  different.  Instead  of  spherical  cells  like  the  egg 
cells,  here  are  produced  cells  resembling  a  miniature  tad- 
pole, with  an  oval  head  and  a  vibrating  tail.  These  are 
the  sperm  cells,  or  sperms,  and  the  enlargement  in  which 
they  are  developed  is  called  a  spermary. 

CLASS   I.  — HYDROZOA. 

Hydroids.  —  Most  of  the  members  of  this  class  are  called 
hydroids,  and,  as  the  name  implies,  they  are  hydralike. 


318 


Descriptive  Zoology. 


But  instead  of  being  simple  most  of  them  are  compound, 
or,  as  it  is  more  commonly  expressed,  they  live  in  colonies. 
We  have  seen  that  hydra  multiplies  by  budding.  Imagine 
a  hydra  in  which  the  budding  continues  indefinitely,  the 
new  individuals  remaining  connected  with  the  parent,  and 


FIG.  182.    A  HYDROID. 

After  Allman.  —  From  Kingsley's  Zoology. 

you  have  the  hydroid  colony.  The  relation  between  these 
members  of  the  colony  is  more  than  a  mere  mechanical 
connection,  for  the  internal  cavity  is  continuous  through  the 
colony,  so  that  whatever  one  individual  takes  as  food  may 
serve  to  nourish  any  one  or  all  the  other  members  of  the 
community. 


Coelenterata.  319 

The  idea  of  community  life  is  well  carried  out  in  that 
there  is  a  well-marked  division  of  labor  among  the  mem- 
bers. Some,  called  nutritive  individuals,  devote  themselves 
to  the  work  of  obtaining  and  preparing  food  for  the  whole ; 
some  develop  the  stinging  cells  and  protect  the  others ; 
while  still  others  are  specialized  for  the  work  of  reproduc- 
tion, and  depend  on  other  members  for  nourishment  and 
protection. 

General  Appearance  of  Hydroids.  —  Most  of  the  hydroids 
are  plantlike  in  appearance,  hence  are  often  called  zoo- 
phytes. Some  resemble  tufts  of  moss,  others  are  simply 
branched  and  trailing  like  the  ground  pine.  They  vary 
greatly  in  color,  from  white  to  dark  brown,  while  some  are 
of  a  beautiful  pink.  A  form  that  will  serve  well  for 
example  is  whitish  or  brownish,  and  forms  a  downy  or 
furry  coating  on  the  wooden  piles  of  wharves,  piers,  etc. 
Many  threads  creep  along  the  surface,  while  others  rise  at 
right  angles  to  the  surface  and  end  in  budlike  swellings. 
Examined  more  closely,  these  terminal  enlargements  are 
found  to  be  bell-shaped.  These  are  the  individuals  borne 
on  the  connecting  and  supporting  stalks.  The  unit,  or 
zooid,  as  it  is  called,  is  very  much  like  a  hydra.  The  body 
is  hollow,  with  a  circle  of  arms  surrounding  the  mouth, 
which  is  at  the  free  end.  It  is  unlike  the  hydra  in  at  least 
three  respects.  First,  the  base,  instead  of  being  closed, 
opens  into  the  supporting  tube,  and  this  is  in  communica- 
tion with  all  the  other  zooids  of  the  colony.  Second,  the 
tentacles  are  solid  instead  of  hollow ;  but  they  are  like  the 
tentacles  of  the  hydra  in  being  flexible  and  provided  with 
stinging  cells  that  serve  for  securing  food.  Third,  the 
mouth  is  distinctly  raised  above  the  bases  of  the  tentacles, 
and  is  capable  of  closing  into  a  cone-shaped  mass,  the 
hypostome,  or  opening  into  a  bell-shaped  entrance. 


'320  Descriptive  Zoology. 

A  Tubularian  Hydroid.  —  The  general  appearance  of  a 
zooid  of  a  tubularian  hydroid  may  be  seen  from  Fig.  182. 
The  body  is  hydralike,  but  with  a  prolonged  mouth.  There 
are  two  layers  of  the  body,  the  ectoderm  and  the  endo- 
derm.  The  ectoderm  -of  the  tentacles  is  provided  with 
nettle  cells. 

Structure  of  the  Stem.  —  The  structure  of  the  common 
stem  is  similar  to  that  of  the  zooid.  The  outer  covering  of 
chitin  is  called  the  perisarc,  while  the  soft  tube  within,  con- 
sisting of  ectoderm  and  endoderm,  is  called  the  cenosarc. 
The  endoderm  cells  have  flagella. 

Action  of  a  Live  Zooid.  —  The  live  zooid  captures  small 
animals  by  stinging  them  as  does  the  hydra.  It  uses  the 
tentacles  to  draw  them  into  the  mouth.  After  the  food  is 
softened  and  reduced  to  a  liquid,  it  is  circulated  by  the 
vibrations  of  the  flagella  of  the  cells  of  the  endoderm.  The 
nettle  cells  serve  for  protection  as  well  as  in  securing  food. 
When  the  zooid  is  disturbed,  it  withdraws  into  the  protect- 
ing cup,  or  hydrotheca,  and  may  thus  remain  for  some 
time. 

Development  of  a  Zooid  —  Budding.  —  The  colony  in- 
creases in  extent  by  budding.  A  bud  forms  on  the  side 
of  a  main  stem.  The  bud  consists  of  the  same  layers  as 
the  stem,  namely,  the  perisarc  and  cenosarc.  The  bud 
swells  into  a  knob,  the  cavity  of  the  main  stem  extending 
into  it,  and  the  nutritive  liquid  circulates  in  the  bud.  After 
a  time  the  perisarc  ruptures  at  the  end  and  expands  into 
the  cup,  the  cenosarc  forms  a  mouth  at  the  end,  tentacles 
develop  around  the  mouth,  and  a  new  zooid  is  complete. 

How  a  New  Colony  is  formed  —  Medusa  Buds.  —  By  a 
continuation  of  the  process  just  described  /the  colony  is 
increased  in  extent,  but  no  new  colony  is  formed,  for  none 


Coelenterata.  321 

of  these  parts  separate  from  the  colony.  But  certain  buds 
differ  from  the  above.  Usually  near  the  base  of  the 
colony  are  to  be  found  longer  buds  which  develop  differ- 
ently. They  become  long  and  club-shaped.  The  soft 
cenosarc,  blastostyle,  develops  circular  side  buds,  called 
medusa  buds,  which  finally  become  detached  and  swim 
away,  passing  out  of  a  hole  which  is  formed  at  the  end  of 
the  gonotheca,  as  the  perisarc  is  here  called. 

Medusae.  —  The  medusa  bud  when  developed  becomes 
an  umbrella-shaped  body,  and  is  called  a  medusa,  or  often 
a  hydromedusa.  It  is,  in  fact,  a  small  kind  of  jellyfish. 
The  outside  of  the  umbrella  is  called  the  exumbrella  and 
the  inside  the  subumbrella."  Hanging  from  the  center  of 
the  subumbrella  surface  is  a  short  handle,  the  manubrium. 
It  is  hollow,  and  the  opening  at  its  end  is  the  mouth.  The 
cavity  extends  up  through  the  handle,  and  continues  as  four 
radiating  tubes  to  the  margin  of  the  umbrella.  These 
four  radiating  tubes,  or  canals,  are  connected  by  a  circular 
canal,  running  around  near  the  margin.  Food  is  taken  in 
at  the  mouth,  digested,  and  circulated  through  this  system 
of  canals.  From  the  margin  of  the  umbrella  a  short  fold 
or  shelf  extends  inward  horizontally,  and  is  called  the  veil 
(velum).  Around  the  margin  are  numerous  tentacles,  and 
on  the  margin  certain  spots  supposed  to  be  organs  of  a 
sense  of  direction.  Some  medusae  have  around  the  mar- 
gin of  the  umbrella  a  series  of  black  spots,  which  are  rudi- 
mentary eyes.  The  umbrella  has  the  power  of  expanding 
and  contracting,  and  by  this  means  the  medusa  swims. 
Sometimes  it  turns  inside  out. 

How  a  Medusa  Multiplies.  —  Suspended  from  the  sub- 
umbrella  surface,  close  to  the  four  radial  canals,  are  four 
spherical  bodies.  These  are  the  gonads.  In  one  indi- 
vidual the  gonads  produce  eggs  (ova),  and  in  another 


322 


Descriptive  Zoology. 


individual  they  produce  sperms.  The  gonads  set  free 
their  contents  in  the  water,  and  the  eggs  are  fertilized  by 
the  sperms.  After  fertilization,  the  egg  develops  first  into 
a  simple  hydralike  polyp,  and  later,  by  budding,  into  a 

branched    hydroid   like  the  form 
that  produced  the  medusa. 

Alternation  of  Generations.  — 
Thus  we  see  that  these  hydroids 
have  two  forms,  and  neither  one  is 
complete.  The  hydroid  form  can 
spread  as  a  colony,  but  it  can  form 
no  new  colony.  But  by  means  of 
the  medusae,  which  are  free-swim- 
ming, it  forms  new  colonies,  which 
may  be  at  a  distance  from  the 
original  colony.  This  peculiar 
process  of  development,  hydroids 
giving  off  medusae,  and  medusae, 
in  turn,  producing  eggs  which 
develop  into  hydroids,  is  known 
as  "alternation  of  generations." 
It  is  found  in  some  other  lower  ani- 
mals, and  among  the  Arthropods. 

Other  Forms  of  Hydrozoa.  —  The 
great  majority  of  Hydrozoa  have 
an  alternation  of  generations  as 
described.  But  there  are  others 
in  which  there  is  only  a  medusa 
form,  no  polyp  form  appearing, 
the  eggs  produced  by  the  medusa 
developing  directly  into  a  medusa  form.  In  others  the 
medusa  buds  are  produced,  but  are  not  set  free.  While 
remaining  attached,  they  produce  and  set  free  the  eggs 


FIG.  183.    PORTUGUESE 
MAN-OF-WAR. 


Coelenterata.  323 

and  sperms,  which  develop  into  polyp  form.  The  siphon- 
ophores  are  in  colonies,  but,  instead  of  being  fixed,  are 
free.  Some  swim  by  means  of  bell-shaped  zooids,  resem- 
bling a  cluster  of  medusae,  while  other  zooids  in  the  group 
devote  themselves  to  nutrition,  and  others  to  the  work  of 
protection.  In  other  kinds  of  siphonophores  there  is  a 
bladderlike  float,  and  locomotion  depends  upon  the  wind 
and  current.  The  Portuguese  man-of-war  is  an  example. 
All  forms  are  well  provided  with  stinging  cells,  and  one 
who  handles  them  carelessly  finds  that  this  whole  branch 
may  well  be  designated  "the  sea  nettles." 


CLASS    II.  — THE    SCYPHOZOA. 

Jellyfishes.  —  This  class  is  mostly  made  up  of  the  larger 
jellyfishes.  One  of  the  most  common  on  the  New  Eng- 
land coast  is  the  common  white  jellyfish,  known  as  Aurelia. 
It  is  saucer-shaped  and  frequently  is  a  foot  or  more  in 
diameter.  It  is  gelatinous  and  semitransparent.  In  the 
center  of  the  subumbrella  is  a  short  stalk,  or  manubrium. 
At  the  end  of  this  is  the  square  mouth,  from  the  corners, 
of  which  extend  four  delicate  processes,  the  oral  arms. 
The  short  gullet  leads  from  the  mouth  to  a  roomy  stomach, 
whose  four  gastric  pouches  extend  halfway  to  the  margin. 
There  are  many  fine  radiating  canals  and  a  small,  circular 
marginal  canal.  On  the  floor  of  each  gastric  pouch  is  a 
brightly  colored  gonad,  whose  contents,  eggs  or  sperms, 
are  "discharged  into  the  stomach  and  pass  out  through  the 
mouth.  Along  the  inner  border  of  each  gonad  is  a  row 
of  delicate  gastric  filaments,  well  supplied  with  stinging 
cells,  whose  function  is  to  paralyze  the  animals  taken  in  as 
food.  The  margin  has  a  fine  fringe  of  tentacles.  Evenly 
distributed  on  the  margin  are  eight  peculiar  sense  organs. 


Descriptive  Zoology. 


Development  of  the  Scyphozoa.  —  The  egg,  after  being 
fertilized,  divides  into  many  cells.  These  finally  arrange 
themselves  into  a  two-layered  sac.  This  becomes  cylin- 
drical and  attaches  itself  by  one  end.  The  other  end 
opens  to  form  a  mouth,  around  which  tentacles  develop, 


FIG.  184.    JELLYFISH. 

The  four  long  projections  are  the  oral  (mouth)  appendages.     The  slender  hanging 
projections  are  the  marginal  tentacles. 

thus  forming  a  hydralike  or  polyp  form.  This  elongates 
and  becomes  constricted  transversely  so  that  it  resembles 
a  pile  of  saucers,  each  of  which  is  scalloped.  These 
saucer-shaped  parts  become  detached  in  order  from  the 


Coelenterata.  325 

top,  each,  except  the  first,  forming  a  jellyfish.     The  sur- 
face that  was  uppermost  becomes  the  subumbrella. 

Other  Jellyfishes.  —  Most  of  the  jellyfishes  are  essen- 
tially similar  to  Aurelia,  though  they  differ  considerably  in 
their  shape,  some  being  conical  instead  of  saucer-shaped. 
They  often  are  seen  in  great  schools,  swimming  lazily  by 
gently  opening  and  closing  the  umbrella,  or  floating  at 
the  surface ;  or  they  may  sink  out  of  sight  at  will.  They 
are  mostly  marine,  and  most  are  free-swimming,  though  a 
few  are  permanently  or  temporarily  attached  by  the  exum- 
brella  surface.  They  are  all  carnivorous,  feeding  largely 
on  Crustacea.  Most  of  them  are  very  beautiful,  being  like 
cut  glass,  or  brightly  colored,  many  being  beautifully  phos- 
phorescent. The  great  blue  jellyfish  of  the  New  England 
coast  sometimes  is  seven  feet  in  diameter  with  tentacles 
a  hundred  feet  long.  Smaller  specimens  of  this  sort,  when 
seen  by  transmitted  light,  as  when  in  an  aquarium, 
resemble  immense  amethysts. 

CLASS   III.  — ACTINOZOA. 

Sea  Anemones.  — To  this  class  belong  the  sea  anemones 
and  most  of  the  coral  polyps.  The  common  sea  anemone 
is  hydralike,  that  is,  it  is  cylindric,  attached  by  the  base. 
The  tentacles  are  numerous  and  are  borne  on  a  disk  sur- 
rounding the  mouth  at  the  free  end.  The  mouth  is  an 
elongated  slit.  The  internal  structure  differs  considerably 
from  that  of  the  hydra.  In  the  first  place,  the  mouth 
does  not  open  directly  into  a  simple  body  cavity,  but  is 
continued  as  a  tubular  gullet,  which  extends  halfway  down 
the  body.  A  series  of  radiating  partitions  run  the  whole 
length  of  the  body,  extending  from  the  outside  of  the 
gullet  to  the  body  wall.  Below  the  lower  end  of  the 


•326 


Descriptive  Zoology. 


gullet  the  free  inner  edges  of  these  partitions,  the  mesen- 
teries, may  be  seen. 

Digestion  in  the  Sea  Anemone.  —  Small  animals,  such  as 
crustaceans,  mollusks,  and  fishes,  which  come  in  contact 
with  the  tentacles,  are  partially  paralyzed.  They  are  then 
drawn  into  the  mouth  and  passed  through  the  gullet  into 
the  digestive  cavity  below,  which  may  perhaps  be  called 


FIG.  185.    SEA  ANEMONE. 

After  Emerton.  —  From  Kingsley's  Zoology. 

the  stomach.  On  the  edges  of  the  mesenteries  below  the 
gullet  are  many  threadlike  projections,  called  the  mesen- 
terial  filaments.  These  filaments  are  richly  provided  with 
nettle  cells,  which  complete  the  killing  of  the  prey.  The 
filaments  are  also  furnished  with  gland  cells,  which  supply 
the  liquid  for  digesting  the  food.  The  liquefied  food  ma- 
terial may  pass  up  into  all  the  spaces  between  the  mesen- 


Coelenterata.  327 

teries^*  or  intermesenteric  spaces,  as  they  are  called. 
There  are  holes  through  the  mesenteries  near  the  top,  so 
these  chambers  may  communicate  with  one  another.  Be- 
tween the  mesenteries  are  ridges,  extending  inward  from 
the  outer  wall,  but  not  reaching  the  gullet.  These  are 
incomplete  or  secondary  mesenteries. 

Change  of  Form  of  the  Sea  Anemone.  —  When  undis- 
turbed the  animal  is  cylindrical,  sometimes  long,  some- 
times broad,  so  that  many  of  them  resemble  the  flowers  of 
the  chrysanthemum,  daisy,  anemone,  and  sunflower.  They 
well  deserve  the  name,  for  many  of  them  are  beautifully 
colored.  The  tentacles  are  often  banded  with  variegated 
colors.  It  is  hard  for  one  who  has  lived  all  his  life  inland 
to  realize  that  such  brilliantly  colored,  flowerlike  forms  are 
actually  animals  and  not  plants.  But  disturb  one  of  these 
flowerlike  animals  and  it  shows  its  real  nature.  It  at 
once  begins  to  shorten,  to  withdraw  its  tentacles,  and 
shrink  into  a  rounded  mass  lying  close  to  its  attachment. 
The  mesenteries  are  well  supplied  with  longitudinal  mus- 
cles, whose  shortening  draws  the  body  down  close.  Near 
the  margin  of  the  disk  are  strong  circular  muscles  which 
shorten  and  shut  in  the  free  end,  over  the  retracted  ten- 
tacles, like  a  bag  with  a  draw-string,  so  that  all  that 
appears  resembles  an  old  felt  hat,  with,  perhaps,  a  little 
indication  of  a  hole  at  the  apex.  After  the  disturbance 
ceases  the  sea  anemone  may  gradually  expand  again. 

Development  of  the  Sea  Anemone.  —  Sea  anemones  lay 
eggs,  which  are  developed  in  the  mesenteries  near  their 
free  edges.  The  later  development  resembles  that  of  the 
jellyfishes,  but  there  is  no  alternation  of  generations. 

General  Characteristics  of  Sea  Anemones.  —  Sea  anem- 
ones are  all  marine.  They  are  all  single,  that  is,  they 
do  not  form  colonies.  They  have  no  true  skeleton.  Some 


328  Descriptive  Zoology. 

sea  anemones  attach  themselves  to  the  shells  inhabited  by 
hermit  crabs.  They  thus  get  transportation,  and  are 
more  secure  of  getting  food.  In  return  they  protect  the 
crab,  for  few  animals  care  to  eat  so  tough  and  nettling  an 
animal  as  a  sea  anemone. 

Coral  Polyps.  —  The  coral  polyps  are  essentially  like 
the  sea  anemone  in  their  structure.  But,  unlike  the  sea 
anemones,  they  are  almost  always  in  colonies.  They  are 
unlike  the  sea  anemone,  too,  in  secreting  carbonate  of  lime 
at  the  base.  The  single  coral  makes  a  cup  or  circular 


FIG.  186.    A  CLUSTER  OF  NEW  ENGLAND  CORAL  POLYPS. 

They  secrete  but  little  coral. 

wall,  with  radiating  partitions,  these  radiating  partitions 
alternating  with  the  mesenteries.  In  the  colonies  these 
individual  cups  fuse  more  or  less  together,  making  im- 
mense masses  of  coral. 

Kinds  of  Coral  Polyps.  —  Coral  polyps  are  usually 
classed  in  two  groups,  according  to  the  number  of  ten- 
tacles. In  the  sea  anemone  the  tentacles  are  some  mul- 
tiple of  six.  Some  authors  call  these  Hexacoralla.  To 
this  group,  besides  the  sea  anemone,  belong  all  the  true 
corals  which  produce  coral  reefs  and  islands.  As  is  well 


Coelenterata.  329 

known,  they  cannot  build  coral  in  cold  water,  being 
limited  to  about  the  temperature  of  60°  F.  The  other 
group  have  the  tentacles  on  the  plan  of  eight,  and  are 
sometimes  therefore  called  Octocoralla.  They  make  little 
coral,  but  form  whiplike  and  fanlike  colonies,  the  sea 


FIG.  187.    RED  CORAL  POLYPS. 

fans,  and  sea  pens,  or  sea  whips.  These  have  a  horny 
core  with  loose  limy  material  on  the  outside.  To  this 
group  belongs  the  well-known  red  coral  of  the  Mediterra- 
nean. The  polyps  of  many  of  the  corals  are  exceedingly 
brilliant. 

GENERAL  CHARACTERISTICS   OF   CCELENTERATA. 

1.  There  is  no  digestive  tube  separate  from  the  body 
cavity. 

2.  Stinging  cells  are  almost  always  present. 

3.  The  body  is  usually  radially  symmetrical,  but  in  some 
there  are  traces  of  bilateral  symmetry. 


330  Descriptive  Zoology. 

4.  In  addition  to  producing  eggs,  many  multiply  by  bud- 
ding, which  often  results  in  (5), 

5.  Colonies,   often    showing   marked  division  of   labor 
among  the  differentiated  individuals,  or  zooids. 

6.  The  body  consists  of  three  layers :  an  ectoderm,  and 
endoderm,  and  a  middle,  supporting  layer,  called  the  meso- 
glea. 

7.  The  ccelenterates  are  mostly  marine. 

CLASSIFICATION   OF   CCELENTERATA. 

Class  i.    Hydrozoa;    examples,  hydra  and  the  hydroids- 

Class  2.  Scyphozoa ;  examples,  most  of  the  large  jelly- 
fishes. 

Class  3.  Actinozoa ;  examples,  the  sea  anemones  and 
most  stony  corals. 

Class  4.    Ctenophora,  the  "  comb  jellies." 


CHAPTER   XXI. 
BRANCH   ECHINODERMATA. 

THE  echinoderms  include  the  starfishes,  brittle  stars, 
sea  urchins,  sea  lilies,  feather  stars,  and  sea  cucumbers,  all 
exclusively  marine. 

CLASS  I.  — ASTEROIDEA. 
Example.  —  The  Common  Starfish. 

Occurrence.  —  The  common  starfish  is  found  all  along 
the  Atlantic  coast  from  Labrador  to  Florida.  It  is  more 
abundant  in  the  shallower  water,  especially  on  the  oyster 
beds.  Other  kinds  of  starfishes  are  found  deeper. 

General  Appearance.  —  The  common  starfish  is  a  five- 
rayed  star.  The  central  body  is  called  the  disk  and  the 
arms  are  the  rays.  In  the  center  of  the  more  flattened 
surface  is  the  mouth ;  hence  this  surface  is  called  the 
"oral"  surface  in  distinction  from  the  opposite  "aboral" 
surface,  which  is  more  convex. 

The  Skeleton.  —  One  of  the  noticeable  features  of  the 
starfish  is  its  roughness.  This  is  due  to  the  limy  skeleton, 
which  consists  of  many  small  pieces  (ossicles)  of  calca- 
reous material  loosely  and,  in  the  main,  irregularly  joined 
together  by  more  or  less  muscular  tissue,  so  that  the  star- 
fish can  turn  or  twist  the  rays  about  to  a  considerable  ex- 
tent. The  skeleton  is  embedded  in  the  tough  body  wall, 
which  is  more  or  less  ciliated,  externally  and  internally. 
Many  of  the  ossicles  bear  rigid  projecting  spines,  while  on 


Descriptive  Zoology. 


the  oral  surface,  especially  along  the  borders  of  the 
grooves  on  the  oral  surfaces  of  the  rays,  are  movable 
spines  attached  to  the  ossicles  of  the  body  wall. 

On  the  aboral  surface  are  many  small  pinchers,  consist- 
ing of  a  short  stalk  bearing  two  calcareous  blades.     The 


FIG.  188.    COMMON  STARFISH. 

stalks  are  flexible,  and  the  blades  of  the  pinchers  may  be 
seen  opening  and  closing.  It  is  thought  they  are  for  the 
purpose  of  keeping  the  body  clean  by  picking  up  and  re- 
moving small  particles.  These  pinchers  are  called  pedi- 
cellariae. 

The  Water  Tube  System.  —  Before  we  can  understand 
how  the  starfish  locomotes  we  must  get  an  idea  of  the 
water  tube  system,  or  water  vascular  system,  as  it  is  usually 
called.  In  the  first  place,  an  examination  of  a  live  starfish 
will  show  the  rows  of  soft,  flexible,  cylindric  tube  feet  in 
the  grooves  in  the  rays.  By  watching  the  live  animal  it 


Echinodermata. 


333 


will  be  seen  that  these  tube  feet  are  retracted,  extended, 
and  variously  moved  about.  For  protection  the  feet  can 
be  withdrawn  into  the  groove.  But  commonly  the  feet 
are  applied  to  the  surface  on  which  the  starfish  is  creep- 
ing. Each  tube  foot  is  a  hollow  cylinder,  containing 
water,  and  is  connected  by  a  slender  tube,  passing  be- 
tween the  ossicles,  with  a  water  bulb  in  the  cavity  of  the 
ray.  Both  the  foot  and  the  bulb  are  muscular,  so  when 
the  bulb  contracts  it  forces  more  water  into  the  foot  and 


.Madreporic 
plate 


Stone  canal 


Radial  canal 

FIG.  189.    WATER  TUBE  SYSTEM  OF  STARFISH. 

extends  it ;  and  when  the  foot  shortens  it  can  send  the 
water  back  into  the  bulb.  Around  the  mouth  is  a  circular 
water  tube,  which  sends  a  tube  along  each  ray ;  and  side 
branches  from  these  radiating  tubes  supply  the  tube  feet. 
On  the  outside  of  the  aboral  surface,  between  the  bases  of 
two  of  the  rays,  there  is  a  wartlike  body.  This  is  the 
madreporic  plate.  It  is  perforated.  Water  enters  it  and 


334  Descriptive  Zoology. 

passes  down  through  a  madreporic  canal  or  stone  canal 
(made  of  the  same  material  as  the  skeleton),  and  this 
stone  canal  empties  into  the  circular  water  tube  around 
the  mouth.  Thus  water,  filtered  through  the  madreporic 
plate,  is  supplied  to  the  whole  water  tube  system.  There 
is  also  a  series  of  water  bulbs  opening  into  the  circular 
water  ring ;  these  are  the  Polian  vesicles. 

How  the  Starfish  Crawls.  —  When  the  starfish  wishes  to 
crawl,  it  distends  the  tube  feet  by  the  action  of  the  water 
bulbs  (or  water  sacs,  called  ampulla)  along  the  inside  of 
the  rays.  The  flattened  disklike  ends  of  the  feet  are 
closely  applied  to  the  surface  on  which  it  is  crawling.  Then 
the  center  of  the  disk  is  somewhat  retracted,  making  a  sort 
of  "  sucker,"  by  which  the  foot  holds  firmly.  When  many 
feet  are  thus  holding  there  is  considerable  power,  and  when 
the  feet  are  now  shortened  the  body  as  a  whole  is  pulled 
along.  The  starfish  can  climb  vertical  walls  or  even  cling 
to  the  under  side  of  a  horizontal  surface.  And  so  strongly 
can  it  hold  that  sometimes,  when  the  collector  tries  to  pull 
it  away  he  simply  tears  the  starfish  in  two.  The  starfish 
can  crawl  with  any  ray  foremost. 

The  Digestive  System  of  the  Starfish.  —  The  mouth  opens 
into  a  large  stomach  which  fills  nearly  all  the  space  in  the 
central  body,  and  has,  in  addition,  a  large  lobe  extending  a 
short  distance  into  each  ray.  The  stomach  is  thin-walled 
and  very  extensible.  This  wide  part  of  the  stomach  is 
called  the  cardiac  portion.  The  stomach  narrows  above, 
and  again  widens  to  form  the  pyloric  portion.  Into  this 
portion  is  poured  the  secretion  of  ten  digestive  glands,  a 
pair  in  each  ray.  The  ducts  of  the  two  glands  in  each 
ray  unite,  so  there  are  five  ducts  entering  the  pyloric 
stomach.  These  glands  are  like  long  bunches  of  small 
grapes.  The  glands  are  held  in  place  by  thin  folds  of  the 


Echinodermata.  335 

lining  membrane  of  the  ray,  and  are  called  mesenteries. 
From  the  pyloric  stomach  a  slender  intestine  extends  up 
to  the  aboral  wall,  a  little  to  one  side  of  the  center.  Its 
opening  is  hard  to  find  and  in  some  starfishes  is  entirely 
obliterated.  There  are  no  jaws  nor  any  teeth  in  the 
starfish. 

The  Starfish's  Food  and  Mode  of  Eating.  —  Starfishes  feed 
chiefly  on  mollusks,  especially  on  oysters  and  mussels. 
The  starfish  arches  the  body  over  the  oyster,  and  then 
turns  its  stomach  inside  out  and  around  the  soft  body  of 
the  oyster,  and,  after  digesting  it,  withdraws  the  stomach 
again.  This  seems  an  odd  way  of  eating,  but  certainly  it 
is  an  economical  way,  for  the  starfish  takes  only  what  it 
can  digest  and  absorb. 

Damage  done  to  Oysters.  —  The  starfish  is  a  very  vora- 
cious animal,  and  the  injury  done  by  it  to  the  oyster  indus- 
try is  very  great.  The  oystermen  have  learned  that  they 
must  make  effort  to  keep  the  oyster  beds  clear  of  starfishes. 

How  Starfishes  recover  after  Mutilation.  —  A  starfish 
torn  in  two  will  grow,  and  may  make  two  complete  star- 
fishes. The  oystermen  know  that  it  will  make  a  bad 
matter  worse  to  tear  the  plunderer  into  pieces  and  throw 
them  back  into  the  water.  Experiments  show  very  great 
power  of  recovery  after  mutilation.  Frequently  one  finds 
starfishes  with  one  ray  missing,  or  even  two  or  three. 
Occasionally  the  collector  finds  a  specimen  with  but  one 
fully  developed  ray,  the  other  four  having  been  lost.  Four 
new  rays  may,  perhaps,  be  started,  which  in1  course  of  time 
will  grow  to  full  size. 

The  Body  Cavity.  —  The  starfish  is  a  decided  advance 
on  the  ccelenterate  type  of  structure  in  having  a  distinct 
body  cavity,  separate  from  the  digestive  tube. 


33 6  Descriptive  Zoology. 

Circulation.  —  There  is  no  well-developed  circulatory 
system,  such  as  we  find  in  the  higher  animals.  There  are 
blood  corpuscles  in  the  liquid  contained  in  the  general  body 
cavity.  This  liquid  pervades  all  parts,  and  is  set  in  motion 
by  the  cilia  of  the  lining  membrane,  and  by  the  general 
movements  of  the  stomach  and  the  bending  of  the  rays ; 
these  movements  seem  to  suffice  to  circulate  the  contained 
liquid,  which  probably  directly  receives  the  absorbed  prod- 
ucts of  digestion. 

Respiration  in  Starfishes.  —  There  is  no  very  complete 
system  of  respiration  in  starfishes.  In  fact,  no  such  system 
is  needed,  for  the  whole  body,  inside  and  out,  is  constantly 
bathed  in  sea  water.  Still,  it  is  thought  by  many  authors 
that  the  tube  feet  are  the  chief  agents  in  absorbing  oxygen 
from  the  water  and  giving  off  the  waste.  There  are  also 
many  holes  through  the  aboral  wall,  from  which  extend 
slender  projections  of  the  thin,  soft  lining  membrane  of 
the  body  cavity.  These  are  now  supposed  to  be  gills. 

The  Nervous  System  and  Senses.  —  The  nervous  system 
is  near  the  surface,  and  can  be  seen  without  dissection. 
Around  the  mouth  is  a  five-angled  nerve  ring,  which  gives 
off  a  radial  nerve  along  each  ray.  It  may  readily  be  seen 
by  separating  the  tube  feet  along  the  middle  line. 

At  the  extreme  end  of  each  ray  is  an  eye  spot,  which 
shows  as  a  distinct  red  spot  in  a  fresh  specimen  of  the 
common  starfish.  In  alcoholic  specimens  it  is  hard  to  see. 

Close  to  the  eye  is  what  appears  to  be  a  tube  foot,  but 
without  the  disk  at  the  end.  This  is  called  a  tentacle,  and 
is  now  believed  to  be  an  organ  of  smell.  The  sense  of 
smell  seems  to  be  a  much  better  guide  than  sight  in  bring- 
ing the  starfish  to  its  food.  There  is  undoubtedly  some 
sensitiveness  to  touch,  but  of  this  and  any  other  senses 
little  is  known. 


Echinodermata. 


337 


Development  of  the  Starfish.  —  The  female  has  a  pair  of 
ovaries  at  the  base  of  each  ray.  They  are  like  slender 
bunches  of  tiny  grapes.  The  eggs  pass  out  of  minute  pores 
in  the  angles  between  the  bases  of  the  rays.  In  the  males 
the  spermaries  occupy  a  similar  position  and  resemble  the 
ovaries  in  form,  but  are  lighter  colored,  usually  white.  The 
young  starfish  goes  through  a  remarkable  transformation, 
the  young  no  more  resembling 
the  adult  than  in  the  case  of 
many  insects  with  which  we 
are  familiar.  The  most  strik- 
ing fact  is  that  the  young  is 
very  distinctly  bilaterally  sym- 
metrical, showing  no  traces  of 
radial  symmetry. 

Other  Forms  of  Starfishes.  — 
Most  starfishes  are  five-rayed, 
but  in  some  the  rays  are  so 
short  that  the  whole  animal  is 
a  pentagon,  the  rays  hardly 

extending  beyond  the  disk.  Some  are  brilliant,  exhibiting 
beautifully  complementary  colors  of  purple  and  orange. 
The  number  of  rays  may  be  as  many  as  twenty.  A  Pacific 
starfish  sometimes  becomes  two  feet  in  diameter. 


FIG.  190. 


BRITTLE  STAR;  SAND 
STAR. 


CLASS  II.—  OPHIUROIDEA. 

The  Brittle  Stars.  —  The  ophiuroids  are  represented  by 
the  brittle  stars.  Their  general  form  is  similar  to  that 
of  the  starfishes.  But  the  central  disk  is  more  distinct  and 
the  arms  relatively  slender.  The  arms  are  more  flexible 
and  the  brittle  star  locomotes  by  active  lateral  movements 
of  the  arms,  making  rapid  progress  compared  to  a  starfish. 


338  Descriptive  Zoology. 

The  arms  are  not  hollow  as  in  the  starfish,  there  is  no 
ambulacral  groove  and  the  tube  feet  project  on  the  side 
instead  of  on  the  oral  surface.  On  account  of  the  taper- 
ing arms,  with  their  active  wriggling  movements,  the 
brittle  stars  are  sometimes  called  serpent  stars.  They 
are  also  called  sand  stars.  In  some  ophiuroids  the  arms 
are  branched  as  in  the  common  basket  star,  whose  arms  are 
many  times  branched,  and  become  so  inrolled  as  to  give 
the  name  basket-fish. 

CLASS   III.  — ECHINOIDEA. 

Occurrence.  —  Sea  urchins  are  found  along  the  Atlantic 
coast  from  low-water  mark  to  fifty  fathoms,  being  more 
common  among  rocks.  They  are  also  found  clinging  to  the 
piles  of  wharves.  The  northern  form  is  greenish,  with 
slender  spines,  somewhat  resembling  a  chestnut  bur.  The 
more  southern  form  is  of  a  dark  color,  with  fewer  and 
stouter  spines. 

General  Form  of  a  Sea  Urchin.  —  The  common  sea  urchin 
is  apple-shaped,  the  mouth  being  where  the  stem  of  an 
apple  is,  and  the  anus  at  the  opposite  end,  or  pole,  as  the 
ends  are  termed.  Running  from  the  mouth  to  the  anus  are 
meridians,  marked  especially  by  the  five  double  rows  of 
tube  feet,  which,  when  fully  extended,  are  long  and  slender, 
reaching  beyond  the  tips  of  the  longest  spines.  For  some 
considerable  space  around  the  mouth  is  a  leathery  mem- 
brane, the  peristome,  where  the  skeleton  is  undeveloped. 

The  Skeleton.  —  As  in  the  starfish,  the  leathery  body  wall 
abounds  in  limy  plates,  or  ossicles ;  but  instead  of  being 
loosely  attached  to  each  other,  as  in  the  starfish,  they  are, 
in  the  sea  urchin,  firmly  cemented  together,  constituting  a 
rigid  shell.  These  shells  are  sometimes  sold  under  the 


Echinodermata. 


339 


name  of  sea  eggs.  In  a  cleaned  shell,  or  corona,  as  it  is 
sometimes  called,  there  are  found  ten  double  rows  of  cal- 
careous plates,  making  twenty  in  all.  Every  alternate 
double  row  is  closely  perforated  for  the  passage  of  the 
tube  feet.  These  perforated  plates  are  called  the  ambu- 


FIG.  191.    SEA  URCHIN. 

The  heavy  projections  are  the  spines;  the  long,  slender  ones  are  the  tube  feet. 

lacral  plates.  Both  the  ambulacral  and  the  interambula- 
cral  plates  bear  rounded  elevations,  on  which  the  spines 
were  borne.  Each  spine  has  a  hollow  in  its  base,  which 
fits  over  an  elevation  on  the  shell,  making  a  ball-and-socket 


340  Descriptive  Zoology. 

joint,  and  is  capable  of  a  limited  motion  in  any  direction 
by  means  of  muscles  attached  around  the  base.  Between 
the  spines  are  the  pincherlike  pedicellariae,  as  in  the  star-- 
fish, only  here  they  have  three  blades  instead  of  two. 

The  Water  Tube  System.  —  The  sea  urchin  has  a  water 
tube  or  water  vascular  system  essentially  like  that  of  the 
starfish.  There  is  a  water  ring  around  the  gullet,  with 
radiating  tubes  between  the  rows  of  feet  along  the  ambu- 
lacral  rows.  Inside  the  shell  are  water  bulbs,  or  ampullae, 
as  in  the  starfish,  and  the  mechanism  for  the  operation  of 
these  parts  is  as  described  for  the  starfish. 

How  the  Sea  Urchin  Locomotes.  — The  injected  feet  are 
extended  and  attached  by  means  of  the  suckerlike  action 
at  the  end  of  each  foot.  Then  the  muscular  shortening  of 
•the  feet  pulls  the  sea  urchin  along.  This  means  of  pro- 
gression is  also  aided  considerably  by  the  movements  of  the 
spines.  The  sea  urchin  can  climb  perpendicular  surfaces. 
When  placed  on  the  aboral  surface,  it  can  turn  over,  though 
it  is  a  very  slow  process.  Sea  urchins  are  sometimes  found 
in  deep  holes  in  rocks,  and  it  is  believed  that  they  have 
gradually  made  the  holes. 

Digestive  System  of  the  Sea  Urchin.  —  Projecting  from 
the  mouth  are  usually  to  be  seen  five  hard,  white  teeth. 
These  teeth  are  movable,  not  being  set  in  sockets,  but  held 
in  a  very  complicated  apparatus,  somewhat  like  a  five-angled 
top,  known  as  Aristotle's  lantern.  The  whole  apparatus  is 
under  muscular  control.  Through  the  center  of  the  whole 
runs  the  gullet.  Above  the  tooth  apparatus  the  intestine 
runs  around  the  body  wall,  then  reverses,  making  in  all 
about  two  and  a  half  turns  around  the  body  wall.  It  then 
extends  up  to  the  apex,  where  it  ends  in  the  anus,  guarded 
usually  by  four  calcareous  plates.  It  is  held  in  place  by 
a  thin  membrane,  the  mesentery. 


Echinodermata.  341 

The  food  is  varied.  Sea  urchins  sometimes  eat  sea- 
weeds. At  other  times  they  are  found  eating  fish,  etc., 
that  have  been  thrown  out  as  refuse  by  the  fishermen. 
Sea  urchins  are  of  no  special  economic  importance,  neither 
being  of  any  use  nor  doing  any  damage. 

Respiration  in  the  Sea  Urchin.  —  Around  the  mouth,  on 
the  leathery  membrane  known  as  the  peristome,  are  some 
specially  modified  tube  feet  which  are  supp9sed  to  act  as 
gills.  But,  as  in  the  starfish,  the  whole  body,  inside  and 
outside,  is  so  thoroughly  bathed  in  water  that  there  hardly 
seems  a  need  of  any  special  organs  of  respiration. 

The  Nervous  System  of  the  Sea  Urchin.  —  This,  too,  is 
very  similar  to  what  we  have  seen  in  the  starfish.  There 
is  a  nerve  ring  around  the  gullet,  from  which  a  radial  nerve 
passes  along  the  ambulacral  line,  between  the  rows  of  tube 
feet,  just  within  the  body  wall. 

At  the  end  of  the  series  of  ambulacral  plates  is  a  single 
plate,  known  as  the  ocular  plate,  on  which  is  an  eye,  at  the 
very  tip  of  each  radial  nerve. 

There  are  also,  over  the  surface  of  the  body,  a  number 
of  small  spherical  bodies,  borne  on  movable  stalks.  These 
bodies  (spheridia)  have  ganglion  cells  in  them,  and  are 
regarded  as  sense  organs. 

Development  of  the  Sea  Urchin.  —  The  ovaries  are  situ- 
ated in  the  aboral  part  of  the  body  cavity  and  are  placed 
in  the  interambulacral  spaces.  A  duct  from  each  ovary 
opens  through  a  plate  at  the  end  of  the  series  of  interam- 
bulacral plates.  These  plates  with  the  genital  pores  are 
called  the  "  genital  plates,"  and  alternate  with  the  ocular 
plates  that  have  been  described  as  occurring  at  the  apex  of 
the  series  of  ambulacral  plates.  In  the  male  the  sperma- 
ries  occupy  a  similar  position,  and  have  similar  genital 
pores.  In  the  Southern  sea  urchin  the  ovaries  are  red 


Descriptive  Zoology. 

from  the  color  of  the  contained  eggs,  while  the  spermaries 
are  white.  The  ovaries  and  spermaries  are  similar  in  form, 
resembling  small  bunches  of  grapes ;  and  if  it  were  not  for 
the  difference  in  color,  it  would  require  microscopic  exami- 
nation to  distinguish  the  two  sexes.  Both  the  eggs  and 
sperms  are  discharged  into  the  water.  The  sperms  are 
microscopic,  tadpole-like  bodies,  swimming  actively  by  the 
vibration  of  their  tails.  If  the  sperms  do  not  gain  access 
to  the  eggs,  the  eggs  do  not  develop,  but  soon  die.  But 
usually  the  sperms  surround  the  eggs,  there  being,  ordi- 
narily, many  sperms  to  each  egg.  One  sperm  gains  en- 
trance to  an  egg,  at  least  the  head  fusing  with  part  of 
the  egg.  The  egg  is  now  said  to  be  fertilized. 

After  fertilization,  the  egg  mass  contracts,  leaving  a 
clear  space  around  it  inside  the  "outer  coat,  or  cell  wall. 
Soon  the  egg  mass  within  divides  into  two  equal  parts, 
each  of  these  halves  again  divides  into  two,  the  four  then 
become  eight,  sixteen,  thirty-two,  and  so  on  until  the  num- 
ber can  no  longer  be  counted  and  the  egg  looks  like  a 
spherical  mulberry.  This  process  of  division  is  known  as 
segmentation.  The  berry  like  mass  now  becomes  hollow, 
consisting  of  a  single  layer  of  cells.  Next  one  side  is 
pushed  in  like  a  rubber  ball  with  one  side  punched  in ; 
it  now  has  a  wall  made  of  two  layers  of  cells.  On  the 
outside  are  little  hairlike  projections  of  the  cells,  called 
cilia,  which  by  their  vibrations  propel  the  body  through  the 
water.  A  set  of  needlelike  rods  develop  within  the 
embryo,  which  soon  make  a  skeleton,  shaped  somewhat 
like  a  common  chair.  This  skeleton  has  a  covering  of  soft 
tissue,  and  the  projections,  which  correspond  to  the  legs  of 
the  chair,  are  covered  with  strong  cilia  for  locomotion. 
The  digestive  tube  has  at  first  but  one  opening,  that  made 
by  the  doubling  in  of  the  outer  wall,  as  above  mentioned, 


Echinodermata. 


343 


and  the  cavity  of  this  depression  forms  the  digestive  cavity. 
The  mouth  is  formed  later  by  a  new  opening  made  through 
the  outer  wall  into  the  first  cavity,  and  the  original  opening 
becomes  the  anus.  So  far  the  young  sea  urchin  is  very 
unlike  the  adult ;  but  after  a  time  this  larva  begins  to 
transform  into  the  real  sea  urchin,  and  soon  the  little  sea 
urchins,  about  the  size  of  pins'  heads,  are  found  crawling 
up  the  sides  of  the  glass  vessels  in  which  they  are  kept.  It 
should  be  noted  that  the  larval  sea  urchin  is  bilaterally 
symmetrical,  whereas  the  adult 
is,  apparently  at  least,  radially 
symmetrical. 

Other  Forms  of  Echinoids.  — 
In  addition  to  the  common 
apple-shaped  sea  urchins,  we 
find  very  greatly  flattened 
forms,  such  as  the  sand  cake, 
or  sand  dollar,  also  called  cake 
urchin.  The  mouth  is  central, 
but  the  anus  is  at  one  edge. 
Slightly  different  is  the  key- 
hole urchin,  with  narrow  open- 
ings through  the  shell  (not 
communicating  with  the  body  cavity).  There  are  some  elon- 
gated urchins,  showing  rather  marked  bilateral  symmetry. 


FIG.  192.    SAND  DOLLAR;  CAKE 
URCHIN. 

The  spines  are  removed  from  most  of 
the  surface. 


CLASS   IV.  —  HOLOTHUROIDEA. 

Sea  Cucumbers.  —  Our  larger  holothurians  are  cucumber- 
shaped,  hence  the  common  name,  sea  cucumber.  The 
mouth  is  at  one  end  and  the  anus  at  the  other.  Around 
the  mouth  is  a  'circle  of  tentacles,  with  which  food  is 
taken.  Along  the  sides,  usually  in  five  distinct  rows,  are 


344 


Descriptive  Zoology. 


the  tube  feet.  Sometimes  the  radial  symmetry  is  more 
or  less  altered,  for  some  of  these  forms  so  habitually  rest, 
or  creep,  on  one  side  that  they  are  said  to  have  a  dorsal 
and  a  ventral  surface.  A  sea  cucumber  may  be  compared 
to  a  sea  urchin  that  has  been  drawn  out  in  the  direction 
of  the  poles  —  that  is,  from  mouth  to  anus  — and  further 
to  have  lost  most  of  the  ossicles  in  the  body  wall  so  that 
it  is  now  flexible  instead  of  being  rigid.  There  are  many 


Tube  feet 


Tentacles 

FIG.  193.    SEA  CUCUMBER. 


microscopic  spicules  in  the  integument  that  give  it  rough- 
ness and  sometimes  some  degree  of  stiffness.  Various 
forms  of  holothurians  are  found  along  the  Atlantic  coast. 
Some  of  the  holothurians  are  so  extremely  elongated  that 
they  are  frequently  mistaken  for  worms.  Among  the 
Chinese  and  other  West  Pacific  peoples,  sea  cucumbers, 
under  the  name  trepang,  are  variously  prepared  for  food. 
They  are  used  principally  for  soups,  and  are  considered 
a  great  delicacy. 


Echinodermata.  345 

CLASS   V.  — THE   CRINOIDEA. 

Sea  Lilies.  —  The  stalked  crinoids  are  borne  on  a  slender 
stalk  of  calcareous  disks,  so  connected  as  to  allow  of  con- 
siderable freedom  of  motion.  The  body  is  flowerlike,  with 

branching  arms  surround- 
ing  the     central    mouth. 
Most  of  the  living  crinoids 
are  found  in  deep  seas, 
and  are   known 
as  the  sea  lilies. 
In  shallow  water 
is  found  a  form 
that  is  stalked  in 
its  earlier  life,  but 
later   the   body, 
with  its  feathery 
arms,  is  set  free 
and     swims     away    by   the 
motions  of  the   arms.     These 
are  known  as  the  feather  stars. 
Crinoids.  —  Many  fossil  crinoids  are 
found  in  the  Mississippi  Valley.    The 
heads  are  less  common,  perhaps  be- 
cause, being  softer,  they  have  been 
ground  to  powder.     But  it  is  common 
•to  find  portions  of  the  stems,  which 
FIG.  194.   A  CRINOID,  OR    look   like  a   series   of  buttons   piled 
one  upon  another,  with  a  more  or 
less  evident  hole  running  through  the 

center.  These  appear  to  have  been  so  abundant  in  the 
seas  of  former  ages  that  they  have  formed  whole  strata  of 
limestone  rock. 


346 


Descriptive  Zoology. 


GENERAL  CHARACTERISTICS   OF   ECHINODERMATA. 

1 .  The  body  and  its  various  organs  are  radially  arranged. 
But  many  show  more  or  less  bilateral  symmetry. 

2.  In  their  development  they  all  undergo  a  marked  meta- 
morphosis, the  young  being  bilaterally  symmetrical,  and 

only  in  a  later  stage  acquiring 
the  radiate  arrangement. 

3.  The  surface  has  an  exoskel- 
eton  of  calcareous  plates,  with 
movable  spines. 

4.  There  is  a  well-developed 
digestive  tube,  distinct  from  the 
body  cavity. 

5.  There  is  a  peculiar  system 
of  water  tubes  by  which  tube  feet 

are  extended  and  locomotion  effected  in  the 
free  forms. 

6.  They  reproduce  by  means  of  eggs,  and 
do  not  bud. 

7.  They  do  not  occur  in  colonies. 

8.  They  are  all  rather  sluggish. 

9.  They  are  all,  without  exception, 
marine. 

10.  They  have  remarkable  power  of 
regeneration  after  mutilation. 

The  echinoderms  were  formerly 
classed  with  the  coelenterates  on  ac- 
count of  the  radial  arrangement  of  the 
parts  of  the  body ;  but  the  echinoderms  differ  sharply 
from  the  coelenterates  in  having  a  digestive  tube  distinct 
from  the  body  cavity,  and  in  having  a  much  higher  devel- 
opment, as  shown  in  the  variety  and  perfection  of  their 


FIG.  195.    STONE  LILY 

(CRINOID). 
From  Packard's  Zoology. 


Echinodermata.  347 

organs.  The  echinoderms  are  a  very  distinct  group, 
standing  apart  from  all  other  branches  of  the  animal 
kingdom. 

CLASSES   OF   ECHINODERMATA. 

Class      I.  Asteroidea  —  Starfishes. 

Class    II.  Ophiuroidea — Sand  Stars  and  Brittle  Stars. 

Class  III.  Echinoidea  —  Sea  Urchins  and  Cake  Urchins. 

Class  IV.  Holothuroidea  —  Sea  Cucumbers,  or  Sea  Slugs. 

Class    V.  Crinoidea  —  Sea  Lilies  and  Feather  Stars. 


CHAPTER    XXII. 
BRANCH    PLATYHELMINTHES. 

The  Flatworms. 

[THE  word  "  worm  "  is  used  in  a  very  loose  and  indefi- 
nite way.  In  popular  language  it  is  applied  indiscrimi- 
nately to  the  legless  earthworm,  the  insect  larva  with 
segmented  appendages  (caterpillar),  and  to  the  elongated 
mollusk  styled  the  shipworm.  All  that  is  required  to 
merit  the  title  is  a  soft,  elongated,  bilaterally  symmetrical 
body.  This  superficial  view  makes  no  distinction  as  to 
whether  the  body  is  segmented  or  unsegmented,  whether 
appendages  are  present  or  absent,  whether  the  form  is 
that  of  an  adult  or  only  in  the  larval  stage,  and  asks  no 
questions  as  to  internal  structure.  The  old  group  of 
"  Worms  "  had  no  fundamental  unity  in  plan  of  structure  ; 
in  fact,  they  had  nothing  in  common  except  a  general  simi- 
larity in  form.  Hence  it  is  natural  that  an  increasing 
knowledge  should  break  up  the  old  branch  "  Vermes." 
In  its  stead  we  find  what  were  formerly  reckoned  as 
classes  of  the  branch  elevated  to  the  rank  of  branches,  as 
follows :  Platyhelminthes,  the  flatworms ;  Nemathelmin- 
thes,  the  roundworms ;  Trochelminthes,  the  rotifers  or 
Wheel  Animalcules  ;  the  Molluscoida  ;  and  the  Annulata, 
the  segmented  or  ringed  worms,  such  as  the  earthworm.] 

The  Platyhelminthes.  —  As  the  name  indicates,  the  body 
is  flattened.  They  are  bilaterally  symmetrical,  and  with- 
out skeleton  or  body  cavity.  There  is  no  system  of  blood- 
tubes.  The  body  has  three  embryonic  layers,  ectoderm, 

348 


Platyhelminthes. 


349 


mesoderm,  and  endoderm.  Many  of  them  are  parasites, 
and  some  wholly  lack  a  digestive  tube.  When  present 
the  digestive  tube  has  but  one  opening,  the  mouth.  They 
show  a  tendency  to  reproduction  by  self-division,  and  most 
of  them  when  cut  in  two  develop  two  individuals. 

The  Tapeworm.  —  Probably  the  most  widely  known  of 
the  flatworms  are  the  tapeworms.  These  are  parasites  in 
the  digestive  tube  of  various  verte- 
brates, including  man.  As  the  name 
indicates,  the  body  is  ribbon-shaped, 
sometimes  attaining  a  length  of  thirty 
feet.  The  body  consists  of  segments, 
or  proglottids,  a  tapeworm  ten  feet 
long  having  about  eight  hundred 
segments.  There  is  no  mouth  nor 
digestive  tube  ;  none  is  needed,  as  the 
worm  lives  surrounded  by  material 
digested  by  another  animal,  and  the 
parasite  simply  absorbs  nourishment 
through  its  skin.  There  is  a  distinct 
head,  whose  chief  work  is  that  of  at- 
taching the  worm  to  the  lining  of  the 
intestine  ;  this  is  secured  by  a  circle 
of  hooks  at  the  end  of  the  head  and 
four  sucking  disks  on  the  sides.  For 
a  short  distance  from  the  head  the  body  is  unsegmented ; 
then  segments  are  formed  by  constrictions  at  intervals ; 
farther  on,  the  segments  grow  larger. 

Development  of  the  Tapeworm.  —  The  hinder  segments 
of  the  tapeworm  contain  embryos.  These  segments  drop 
off  and  the  embryos  are  set  free,  passing  out  with  the 
excrement.  They  are  eaten  by  another  animal,  the  hog, 
for  instance;  in  the  intestine  the  embryo  bores  through  the 


FIG.  196.    TAPEWORM 
(  Tcenia  solium) . 

In  upper  left  hand  corner  of 
figure  the  head  much  mag- 
nified. After  Leuckart.  — 
From  Jordan  and  Kel- 
logg's  Animal  Life. 


350  Descriptive  Zoology. 

wall  of  the  intestine  into  the  muscles  or  other  tissues. 
Here  it  becomes  flask-shaped  (bladder  worm)  and  develops 
a  head  with  hooks  and  suckers ;  but  in  this  condition  it 
must  remain  unless  eaten  by  some  other  animal.  If  the 
flesh  be  cooked,  the  bladder  worm  (cysticercus)  will  be 
killed.  The  danger  comes  in  eating  raw  or  half-raw  meat. 
If  taken  into  the  intestine  of  another  animal,  it  attaches 
by  hooks,  or  suckers,  or  both,  and  the  body  elongates  by 
the  formation  of  segments  as  above  noted. 

Kinds  of  Tapeworms.  —  Man  is  infested  by  at  least 
three  different  kinds  of  tapeworms,  —  one  obtained  from 
pork,  another  from  beef,  and  a  third  from  fish ;  but  the 
latter  kind  is  seldom,  if  ever,  found  in  this  country. 

Various  animals  have  their  own  kinds  of  tapeworms, 
usually  getting  them  from  a  certain  kind  of  animal  on 
which  they  prey ;  thus  the  dog  has  tapeworms  which 
have  passed  their  larval  stage  in  the  muscles  of  the  rabbit. 
The  cat  gets  a  tapeworm  from  the  mouse. 

The  Liver  Fluke.  —  This  is  another  of  the  flatworms.  It 
is  a  parasite  in  the  liver  of  the  sheep,  living  in  the  larger 
bile  ducts.  The  eggs  develop  into  embryos  which  escape 

with  the  excrement. 
Then  they  pass  into  the 
bodies  of  snails.  Here 
they  reach  the  larval 
stage.  After  leaving  the 

snail,  they  attach  them- 
FIG.  197.    LIVER  FLUKE.  * 

Atrematodeworm.  SelvCS      tO      damP      SraSS 

under  water.     If   eaten 

by  sheep,  they  become  fully  developed  worms  like  the  adult 
from  whose  eggs  they  developed.  In  England  it  was  esti- 
mated that  3,000,000  sheep  were  killed  by  the  liver  fluke  in 
1880,  and  that  the  average  yearly  loss  is  1,000,000. 


Nemathelminthes.  351 

CLASSES  OF   PLATYHELMINTHES. 

[Class  i.   Trematoda  —  Liver  Fluke. 
Platyhelminthes.  .-j  Class  2.   Turbellaria  —  (ciliated). 
[  Class  3.    Cestoda  —  Tapeworm. 

BRANCH  NEMATHELMINTHES. 

THE   ROUNDWORMS. 

The  roundworms  have  long,  cylindrical  bodies.  They 
are  not  segmented,  but  some  of  them  have  the  appear- 
ance of  segmentation.  Some  are  parasites  in  animals  and 
plants,  while  others  live  a  free  life.  Most  of  the  round- 
worms  belong  to  the  class  Nematoda. 

Hair  Worms.  —  These  are  often  found  as  parasites  in 
grasshoppers  and  other  insects,  but  later  they  live  free 
outside.  They  are  by  many  ignorant  people  believed  to 
be  horsehairs  that  have 
"come  to  life"  by  soaking 
in  water. 

The  Vinegar  Eel. —This  is 

another    small   roundworm 

.  .  ,     .  FIG.  198.    HAIR  WORM. 

which  is  well  known. 

Intestinal  Worms.  —  Two  forms  of  roundworms  are  not 
uncommon  in  the  human  intestine,  especially  in  those  of 
children.  The  eggs  or  larvae  have  been  swallowed  with 
food.  The  pinworm  is  well  known  ;  it  is  small  and  white 
and  usually  inhabits  the  rectum.  The  other  is  larger, 
sometimes  somewhat  resembling  an  earthworm  in  size  and 
general  appearance,  though  lacking  the  segments.  It 
belongs  to  the  genus  Ascaris. 

Trichina.  —  The  most  dangerous  of  the  parasitic  round- 
worms  is  Trichina.  It  is  small,  not  exceeding  an  eighth 


35* 


Descriptive  Zoology. 


of  an  inch  in  length.  It  is  sometimes  called  the  "  pork- 
worm."  As  is  well  known,  this  parasite  is  obtained  by 
eating  raw  or  partially  raw  pork,  and  there  is  no  danger 
when  the  flesh  is  thoroughly  cooked.  If  they  gain  access 
to  the  intestine  of  the  pig,  the  females  bring  forth  alive  a 


FIG.  199.    TRICHINA  ENCYSTED  IN  HUMAN  MUSCLE. 

Highly  magnified.  —  From  Packard's  Zoology. 

large  number  of  young.  These  bore  their  way  outward 
into  the  muscles  and  there  inclose  themselves  in  a  sac  or 
capsule,  where  they  may  remain  an  indefinite  time.  If 
this  pork,  uncooked,  is  eaten  by  man,  the  capsule  is  di- 
gested and  the  larvae  are  set  free.  The  young  soon  bore 
through  into  the  muscles  and  each  worm  gets  into  a  muscle 
cell  and  coils  up  in  a  case  or  "cyst,"  which  it  forms  for 
itself. 

The  Guinea  Worm.  —  In  the  East  Indies  occurs  another 
parasite,  the  guinea  worm.  It  is  sometimes  found  two 
feet  long,  embedded  in  the  connective  tissue  under  the 
human  skin.  It  is  supposed  that  the  eggs  or  larvae  are 
introduced  in  drinking  water. 

BRANCH   TROCHELMINTHES. 

THE    ROTIFERS. 

The  Wheel  Animalcule.  —  The  word  "Rotifer"  means 
wheel  bearer,  from  the  two  circular  disks  at  the  anterior 
end,  around  the  borders  of  which  are  circles  of  cilia  whose 


Molluscoida.  353 

motions  resemble  the  rotation  of  a  wheel.  These  disks 
can  be  retracted  when  the  animal  wishes.  The  common 
name  for  one  of  these  animals  is  the  "  wheel  animalcule." 
As  implied  by  the  term  animalcule,  the  animals  are  small, 
usually  not  exceeding  a  thirtieth  of  an  inch  in  length. 
They  occur  in  fresh  water,  and  are  usually  to  be  found 
when  looking  over  minute  water  plants  under  the  micro- 
scope. They  are  transparent  and  are  easily  examined,  all 
their  organs  showing  without  dissection.  Though  small, 
they  are  highly  organized,  having  a  complete  digestive 
system,  the  food  being  swept  to  the  mouth  by  the  cilia 
bordering  the  disks.  There  is  also  a  nervous  system,  with 
one  or  more  eyes. 

They  can  swim  by  the  action  of  the  cilia  and  they  also 
progress  by  a  looping  movement,  attaching  alternately  by 


FIG.  200.    WHEEL  ANIMALCULE  (ROTIFER). 

From  Packard's  Zoology, 

the  two  ends  of  the  body.  The  posterior  part  of  the  body 
is  a  segmented  "  tail "  which  can  be  withdrawn  like  a 
telescope.  It  is  said  that  after  being  dried  for  years, 
they  -will  revive  when  placed  in  favorable  conditions,  though 
some  authors  think  it  is  contained  eggs  that  survive  instead 
of  the  adults. 

BRANCH   MOLLUSCOIDA. 

This  group  gets  its  name  from  the  fact  that  some  of  the 
forms  were  once  supposed  to  be  mollusks.  There  are  two 
principal  classes. 


354 


Descriptive  Zoology. 


The  Polyzoa. — These  are  chiefly,  though  not  entirely,  ma- 
rine and  are  known  as  the  "sea  mats"  or  "corallines." 
They  are  also  known  as  the  "moss  animals."  These 
names  come  from  the  fact  that  they  grow  in  colonies  like 
mosses.  They  often  incrust  rocks  with  their  skeletons, 
which  are  either  gelatinous,  chitinous,  or  calcareous. 
Each  individual  is  frequently  contained  in  a  sort  of  cup, 
into  which  it  can  retract  or  from  which  it  can  protrude  to 
a  certain  extent.  There  is  a  row  of  tentacles  around  the 
mouth.  One  of  our  fresh-water  forms  (Pectinatella)  has  a 
gelatinous  basis  or  common  body,  which  is  found  in  spher- 
ical masses  as  large  as  a  man's  head, 
being  attached  to  branches  in  the  water. 
The  living  animals  are  on  the  outside. 
Such  masses  are  often  called  "sponges" 
by  the  fishermen. 

The    Brachiopods.  —  These    are   in- 
closed in  a  bivalve  shell,  and  are  named 
the  "  lamp  shells."     Their  resemblance 
to    mollusks    is  very    superficial,    the 
FIG.  201.    LAMP  SHELLS  internal   structure    of    the   two   being 

(BRACHIOPODS).  ^^jjy      un]ike  There       ig      usuaUy     a 

circle  of  tentacles  somewhat  as  in  the  Polyzoa.  The 
brachiopods  are  exclusively  marine.  They  are  attached 
by  a  stalk  which  extends  through  the  larger  valve  near  the 
hinge.  There  are  many  fossil  brachiopods. 


CHAPTER    XXIII. 
CLASSIFICATION   OF   THE  ANIMAL   KINGDOM. 

(Parker  and  Haswell.) 

BRANCH  I.  —  PROTOZO'A. 

Class     I.  Rhlzop'oda  —  Amoe  ba,  Globigeri'na. 

Class    II.  Mastigoph'ora —  Eugle'na,  Vol'vox,  Noctil'uca. 

Class  III.  Sporozo'a —  Gregari'na. 

Class    V.  Infuso'ria —  Parame'cium,  Vorticel'la. 

BRANCH  II.  —  POR!F'ERA. 
Class     I.    PorTfera —  sponges,  fresh-water  and  marine. 

BRANCH  III.  —  CffiLENTERA'TA. 

Class     I.  Hydrozo'a  —  Hy'dra,  sea  anemone. 

Class    II.  Scyphozo'a — jellyfish. 

Class  III.  Actinozo'a  — corals. 

Class  IV.  Ctenoph'ora  (ten-off-o-ra)  —  comb  jellies. 

BRANCH  IV.  —  PLATYHELMIN'THES. 

Class     I.    Turbella'ria  —  planarian  worms. 
Class    II.    Tremato'da  —  liver  fluke. 
Class  III.    Cesto'da  —  tapeworm. 

BRANCH  V.  — NEMATHELMIN'THES. 
Class     I.    Nemato'da  —  roundworms,  Trichina. 

BRANCH  VI.  —  TROCHELMIN'THES. 

Class     I.    Rotlfera  —  wheel  animalcules. 
355 


356 


Descriptive  Zoology. 
BRANCH  VII.  —  MOLLUSCOI'DA. 


Class     I.   Polyzo'a —  sea  mats. 

Class    II.    BrachiSp'oda  —  lamp  shells. 


BRANCH  VIII.  — 


Asteroi'dea  —  starfish. 
Ophiuroi'dea  —  brittle  stars. 


Class     I. 

Class   II. 

Class  III.    Echinoi'dea —  sea  urchins. 

Class  IV.    Holothuroi'dea —  sea  cucumbers. 

Class    V.    Crinoi'dea —  sea  lilies. 


BRANCH  IX.  — ANNULA'TA. 

Class     I.   Chsetop'oda  (ke-top'-o-da) —  earthworm. 
Class    II.   Gephyre'a  (jef-e-re'-a). 
Class  III.    Hn-udin'ea  — leech. 


Class     I. 

Class   II. 

Class  III. 
Order 
Order 
Order 
Order 
Order 
Order 
Order 
Order 
Order 

Class  IV. 


BRANCH  X.  —  ARTHROP'ODA. 

Crusta'cea  —  crayfish,  crab,  barnacle,  cyclops. 

Myrlap'oda —  centiped,  milliped. 

Insec'ta —  grasshopper,  dragon  fly,  water  bug,  butterfly. 

Thysanu'ra —  small,  wingless  insects. 

Orthop'tera —  grasshopper,  cricket,  cockroach. 

III.  Odona'ta  —  dragon  fly,  damsel  fly. 

IV.  Hemfp'tera  —  water  bug,  squash  bug,  cicada. 
Neurop'tera  —  ant-lion. 

Lepidop'tera  —  butterfly,  moth. 
DTp'tera  — housefly,  horse  fly,  flesh  fly,  mosquito. 
Coleop'tera  —  May  beetle,  potato  beetle,  tiger  beetle. 
Hymenop'tera  —  bee,  wasp,  ant,  gallfly,  ichneumon  fly. 


V 

VI 

VII 

VIII 

IX 


Arach'nTda  —  spiders,  ticks,  mites,  daddy  longlegs. 


BRANCH  XL  —  MOLLUS'CA. 

Class     I.  Pelecyp'oda  —  clam,  oyster,  scallop,  mussel. 

Class   II.  Amphineu'ra  —  chl'ton  (ki'-ton). 

Class  III.  Gastrop'oda  —  snails,  fresh-water  and  marine. 

Class  IV.  Cephalop'oda  —  squid,  cuttlefish,  oc'topus,  nau'tilus. 


Classification  of  the  Animal  Kingdom.       357 

BRANCH  XII.  — CHORDA'TA  (kor-da'-ta). 

Subbranch     I.    Adelochor'da — Balanoglos'sus. 
Subbranch    II.    Urochor'da  —  sea  squirts. 
Subbranch  III.   Vertebra' ta. 

Division  A.    Acra'nia  (without  cranium)  —  lancelet. 
Division  B.    Crania'ta —  all  other  vertebrates. 
Class     I.    Cyclostom'ata —  lamprey  eels. 
Class   II.    PIs'ces  (pts'-sez) —  fishes. 

Subclass     I.    Elasmobran'chii  —  shark,  ray. 
Subclass   II.    Hdloceph'ali  — Chimera. 
Subclass  III.    Teleos'tomi. 

Order     I.    Crossopterygii  —  Polyp'terus. 

Order   II.    Chondrostei  —  sturgeon. 

Order  III.    Holostei  — gar  pike,  dogfish  (of  Central  states). 

Order  IV.    Teleos'tei —  most    bony   fishes,    such    as    catfish, 

salmon,  herring,  mackerel,  codfish,  perch. 
Subclass  IV.    Dip  noi —  lungfish. 
Class  III.    Amphib'ia. 

Order     I.    Urode'la —  mud  puppy,  siren,  salamander. 
Order   II.    Anu'ra  —  frog,  toad. 
Order  III.    Gymnophio'na —  blind  snake. 
Class  IV.    Rgptfl'ia. 

Order     I.    Squama'ta —  lizard,  snake. 
Order   II.    Chelo'nia  (ke-lo'-ni-a)  —  turtle. 
Order  III.    Crocodll'ia  —  alligator,  crocodile. 
Class    V.    A'ves. 

Division  A.    Rati'tae  (breastbone  without  keel)  —  emu,  ostrich. 
Division  B.    Carina'tae  (breastbone  keeled). 
Order        I .    Pygop'odes  —  loon,  grebe. 
Order      II.    Impen'nes  —  penguins. 
Order     III.    Turbina'res  —  pet/rels. 
Order     IV.    Steganop'odes  —  cormorant,  pelican. 
Order      V.    Herodio'nes  —  heron,  stork. 
Order     VI.    An'seres  —  duck,  goose. 
Order   VII.    AccTp'itres  —  hawk,  owl,  vulture. 
Order  VIII.    Crypturi  —  tinamou. 
Order     IX.   Galll'nae  —  grouse,  quail,  turkey. 
Order      X.    Gral'lae  —  rail,  crane. 
Order     XI.    Ga'vias  —  gull,  tern. 


358 


Descriptive  Zoology. 


Order      XII.    Limlc'olae  —  snipe,  plover. 
Order     XIII.    Pterocle'tes  —  sand  grouse. 
Order     XIV.    Colum'bae  —  pigeon,  dove. 
Order       XV.   Psit'taci  (sit'-a-si)  —  parrot,  cockatoo. 
Order     XVI.    Stri'ges  (stri'-jez)  —  owls. 
Order   XVII.    Pica'riae  —  woodpecker,  cuckoo,  humming  bird. 
Order  XVIII.    Pas'seres  —  robin,  lark,  sparrow,  thrush,  crow. 
Class  VI.    Mamma'lia. 

Subclass    I.    Protothe'ria —  duckbill,  spiny  ant-eater. 
Subclass  II.    The'ria. 

Section  A.    Metathe'ria  (marsupials)  —  opossum,  kangaroo. 
Section  B.   Euthe'ria. 

Order        I.   Edenta'ta —  sloth,  ant-eater 
Order       II.    Ceta'cea —  whale,  porpoise,  dolphin. 
Order     III.    Sire'nia — manatee,  dugong. 
Order     IV.    Ungula'ta:- 

Odd-toed    (PerTssodac'tyls)  —  horse,  tapir,  elephant. 
Even-toed  (Artiodac'tyls)  —  ox,  sheep,  deer,  pig. 
Order       V.    Carnlv'ora  —  dog,  cat,  bear,  wolf,  fox,  seal. 
Order     VI.    Roden'tia  —  rat,  mouse,  rabbit,  squirrel, 
Order   VII.    Insectiv'ora  —  mole,  shrew,  hedgehog. 
Order  VIII.   Chirop'tera  —  bat. 
Order     IX.   Prfmates  —  lemur,  baboon,  ape,  man. 


INDEX   TO    PART    I. 


Abalone,  136. 

Abdomen  of  grasshopper,  2. 

Aboral  surface  of  starfish,  331. 

Acrania,  148,  153. 

Actinozoa,  325. 

Adaptation,  15. 

Adelochorda,  148. 

Air  bladder  of  fish,  155,  163. 

Sacs  of  grasshopper,  5. 
Of  pigeon,  216. 
Of  snake,  201. 

Tube  of  grasshopper,  5. 
Albatross,  226. 
Albumen,  219. 
Alligator,  206. 

Gar,  177. 
Alternation  of  generations,  322. 

In  tunicates,  151. 
Ambulacral  plate,  339. 
Ammonites,  144. 
Amoeba,  286. 

Dividing,  289. 

Encysted,  289. 
Amphibia,  181. 
Amphioxus,  151. 
Amphipoda,  84. 
Ampullae,  333. 
Angle,  facial,  282. 
Animalcule,  bell,  294. 

Slipper,  291. 

Wheel,  352,  353. 
Annulata,  87. 
Anolis,  197. 
Ant,  50,  51. 

Ant-eater,  256,  257,  260. 
Ant  lion,  24. 
Antelope,  273. 
Antenna  of  grasshopper,  4. 
Anthropoidea,  282. 
Antidote  for  snake  bites,  204. 
Antlers,  274. 
Anura,  195. 


Aortic  arches  of  earthworm,  95. 

Aperture  of  snail  shell,  127. 

Apes,  282. 

Aphids,  23,  50. 

Appendix  vermiformis,  283. 

Arachnida,  55. 

Arches,  aortic,  95. 

Aristotle's  lantern,  340. 

Armadillo,  259,  260. 

Arms,  oral,  of  jellyfish,  323,  324. 

Of  squid,  139. 
Arrowfish,  140. 
Arteries  of  crayfish,  68. 
Arthropoda,  i,  54,  77,  86. 
Artificial  selection,  218. 
Artiodactyls,  267,  269. 
Ascaris,  351. 
Ascidians,  148,  149. 
Assimilation  in  amoeba,  290. 
Asteroidea,  331,  347. 
Auks,  225. 
Aurelia,  323. 
Automatic  action,  289. 
Aves,  208. 

Badger,  282. 
Balancers,  32,  36. 
Balanoglossus,  148. 
Baleen  plates,  265. 
Barb  of  feathers,  208. 
Barbadoes  earth,  299. 
Barbels  of  catfish,  173. 
Barbules  of  feather,  208. 
Bark  lice,  24. 
Barnacles,  81,  82. 
Basket  fish,  338. 

Star,  338. 
Bass,  166. 
Batrachia,  181. 
Bats,  264,  265. 
Beach  fleas,  84. 
Beak  of  pigeon,  214. 

359 


36° 


Index. 


Beak  of  squid,  141. 
Bear,  279,  280,  281. 
Beavers,  262. 
Bedbug,  24. 
Bee  glue,  47. 
Bees,  short-tongued,  49. 
Bell  animalcule,  294. 
Belostoma,  20. 
Benacus,  20. 
Bend  of  wing,  209. 
Berry  lobster,  74. 
Bighorn  sheep,  270. 
Bile  duct  of  pigeon,  215. 

Sac  of  snake,  201. 
Bill  of  woodpecker,  237. 
Bird,  external  features  of,  210. 
Birds,  fossil,  242. 

Game,  244. 

Value  of,  244. 
Bison,  272. 
Bittern,  229. 
Black  bass,  172. 
Blackbirds,  239. 
Black  snake,  200. 
Black  tail  deer,  274,  275. 
Bladder  of  crayfish,  70. 

Urinary,  of  perch,  157. 
Bladder  worm,  350. 
Blastostyle,  321. 
Blind  snake,  195. 
Blister  beetle,  41,  52. 
Blood  of  earthworm,  94. 
Blood  tubes  in  earthworm,  94. 
Blowfly,  35. 
Bluebird,  240,  241. 
Blue  racer,  200. 
Bobcat,  279. 
Bobolink,  239. 
Bob-white,  231. 
Body  cavity  of  earthworm,  89. 

Of  hydra,  314. 

Of  starfish,  335. 
Borers,  40. 
Botfly,  35. 
Bowfin,  178. 
Boxshell  turtle,  205. 
Brachiopods,  354. 
Brachyura,  84. 
Braconids,  52. 
Brain  of  fish,  285. 


Brain  of  mouse,  285. 

Of  pigeon,  217. 

Of  snake,  285. 

Of  sparrow,  285. 

Of  toad,  285. 

Of  vertebrates,  285. 
Branchiostegal  membrane,  160. 
Branchiostoma,  151. 
Breastbone  of  pigeon,  211. 
Bristles  of  earthworm,  90. 
Brittle  stars,  331,  337. 
Brood  comb,  47. 
Browsing,  277. 
Bud  of  hydra,  314. 
Budding  of  hydra,  317. 

Of  hydroid,  320. 
Buffalo,  272. 
Buffalo  fish,  166, 173. 
Bugs,  20. 
Bulb,  spinal,  285. 
Bumblebees,  49. 
Butcher  bird,  240. 
Byssus,  119,  125. 

Cabbage  butterfly,  27. 

Cake  urchin,  343. 

Calcareous  sponge,  308. 

Camel,  277. 

Canal,  marginal  of  jellyfish,  323. 

Canvasback,  228. 

Capsule,  egg,  of  earthworm,  88. 

Thread  of  hydra,  315. 
Carapace,  205. 
Carinatae,  222,  223. 
Carnivora,  278. 
Carp,  166,  173. 
Carpet  beetles,  41. 
Carrion  beetles,  41. 

Crow,  236. 

Eaters,  217. 
Cassowary,  222. 
Catbird,  240. 
Catfish,  166,  173. 
Cats,  278. 
Caucasian,  282. 
Ceca  of  grasshopper,  7,  9. 

Of  perch,  157. 

Of  pigeon,  216. 
Cecropia,  30. 
Cecum  of  man,  283. 


Index. 


361 


Cecum  of  rabbit,  250. 
Cell,  301. 

Wall,  301. 
Celom,  89. 

Cenosarc  of  hydroid,  320. 
Centiped,  54. 

Skein,  55. 
Cephalization,  80. 
Cephalopods,  138. 
Cerebellum,  285. 
Cerebrum,  285. 
Cestoda,  351. 
Chalk,  298. 
Chameleon,  198. 
Channel  cat,  173. 
Chickadee,  241. 
Chimney  swallows,  238. 
Chinch  bug,  23. 
Chipmunk,  262. 
Chitin,  84. 
Chiton,  136. 
Chordata,  148,  246,  284. 
Chromatophores  of  squid,  141. 
Cicada,  20,  22. 
Cilia  of  earthworm,  96. 

Of  paramecium,  293. 

Of  rotifer,  353. 

Of  vorticella,  295. 
Ciliated  chambers,  308,  310. 
Circulation  in  clam,  116. 

In  crayfish,  68. 

In  earthworm,  94. 

In  frog,  184. 

In  grasshopper,  6. 

In  perch,  157,  159. 

In  pigeon,  216. 

In  rabbit,  251. 

In  snail,  130. 

In  snake,  202. 

In  squid,  142. 

In  starfish,  336. 
Cirripedia,  83. 
Clam,  foot  of,  105. 

Fresh-water,  102. 

Giant,  125. 

Hard,  121. 

Long,  120. 

Muscles  of,  109. 

Razor-shell,  124. 

Round,  121. 


Clam,  siphons  of,  105,  108. 

Soft,  1 20. 
Clam  shell,  102, 103. 

Growth  of,  no. 

Structure  of,  109,  no. 
Clavicle  of  pigeon,  213. 
CJaws  of  cat,  278. 

Of  dog,  279. 
Click  beetles,  41. 
Climbing  birds,  237. 
Clitellum  of  earthworm,  88. 
Cloaca  of  pigeon,  216. 

Of  snake,  201. 

Of  sponge,  310. 
Cloven-footed  animals,  269. 
Clypeus  of  grasshopper,  2. 
Cochineal  insect,  24,  52. 
Cockatoo,  237. 
Cockroaches,  13. 
Cocoons  of  ants,  50. 

Of  lepidoptera,  30. 

Of  spider,  59. 
Codfish,  165,  172. 
Codling  moth,  30. 
Coelenterata,  313. 
Cold-blooded  animalsj  291. 
Coleoptera,  36,  43, 
Collar  bones  of  pigeon,  213. 
Colon,  ascending,  283. 

Descending,  283. 

Transverse,  283. 
Colonial  protozoans,  305: 
Colony  of  hydroids,  318. 
Color  dimorphism,  235. 

Of  fishes,  164. 

Of  frog,  185. 

Of  jellyfishes,  325. 

Of  rabbit,  252. 

Of  squid,  141. 
Colorado  potato  beetle,  39. 
Colors  of  birds,  219. 
Commercial  sponge,  309,  310. 
Conchology,  146. 
Condor,  236. 

Condyle,  occfpital,  in  bird,  243. 
Conjugation  of  protozoans,  297. 
Constrictors,  200. 
Contour  feathers,  209. 
Contractile  vacuole,  286,  287,  295. 
Contractility,  289. 


362 


Index. 


Copepoda,  83. 
Copperhead,  203. 
Coracoid  bone,  214. 
Coral  islands,  328. 

Polyps,  325,  328. 

Red,  329. 

Reefs,  328. 
Corallines,  354. 
Cord,  spinal,  285. 
Cormorant,  227. 
Corpuscles  of  birds,  245. 

Of  earthworm,  94. 
Cougar,  279. 
Cow,  269. 
Cowbird,  220,  239. 
Coxa  of  grasshopper,  2,  4. 
Coyote,  279. 
Crabs,  78. 

Development  of,  79. 

Fiddler,  80. 

Hermit,  81. 

Horseshoe,  85. 

King,  85. 

Oyster,  79, 80. 

Sand,  80. 

Swimming,  79. 
Crab's  eyes,  75. 
Crampfish,  170. 
Cranes,  230. 
Craniata,  148,  153. 
Crayfish,  61,  65. 

Blind,  81. 

Distribution  of,  76. 

Enemies  of,  73. 

Holes,  61. 
Crayons,  299. 
Crickets,  13. 
Crinoidea,  345,  347. 
Crocodiles,  206,  207. 
Crop  of  earthworm,  89,  93. 

Of  grasshopper,  7. 

Of  pigeon,  214,  215. 
Croton  bug,  13. 
Crows,  239. 

Carrion,  236. 
Crustacea,  61. 
Cubs,  281. 
Cuckoos,  221,  237. 
Cud  chewers,  269. 
Gunner,  171. 


Curculios,  41. 
Currant  worm,  51. 
Cuticle  of  vorticella,  295. 
Cuttlefish,  145. 
Cyclops,  83,  84. 
Cyclostomata,  148,  153. 
Cyst,  289. 

Cyst  of  trichina,  352. 
Cysticercus,  350. 

Daddy  longlegs,  60. 

Damsel  flies,  13. 

Darning  needles,  14. 

Darters,  171. 

Decapoda,  84. 

Deer,  273,  274. 

Deer  flies,  34. 

Development  of  ascidians,  149. 

Of  clams,  118. 

Of  crabs,  79. 

Of  earthworm,  97. 

Of  frog,  187,  189. 

Of  grasshopper,  10. 

Of  honey  bee,  47,  48. 

Of  house  fly,  32. 

Of  hydroid,  320. 

Of  jellyfish,  324. 

Of  lepidoptera,  28. 

Of  metazoa,  302. 

Of  oyster,  122. 

Of  perch,  162. 

Of  rabbit,  254. 

Of  retrograde,  150. 

Of  sea  anemone,  327. 

Of  sea  urchin,  341. 

Of  sponge,  311. 

Of  starfish,  337. 

Of  tapeworm,  349. 

Of  vorticella,  296. 
Devilfish,  170. 
Devil's  needles,  14. 
Dewclaws,  269. 
Diamond  rattlesnake,  203. 
Diaphragm  of  rabbit,  249,  251. 
Differentiation,  304. 
Digestion  in  amoeba,  290. 

In  crayfish,  65. 

In  hydra,  316. 

In  sea  anemone,  326. 
Digestive  gland  in  clam,  115. 


Index. 


363 


Digestive  gland  in  starfish,  334. 
Digestive  system  of  clam,  115. 

Of  crayfish,  65. 

Of  earthworm,  89,  92. 

Of  frog,  181,  183. 

Of  grasshopper,  7. 

Of  perch,  156. 

Of  pigeon,  214. 

Of  rabbit,  250. 

Of  sea  urchin,  340. 

Of  snail,  129. 

Of  snake,  200,  201. 

Of  squid,  141. 

Of  starfish,  334. 
Digitigrade  animals,  280. 
Dingo,  259. 
Diphycercal  tail,  162. 
Diplocardia,  95. 
Dipnoi,  180. 
Diptera,  32. 
Discoid  shell,  128. 
Disk  of  starfish,  331. 

Of  tapeworm,  349. 
Distribution  of  crayfishes,  76. 

Of  earthworms,  97. 

Of  feathers,  209. 

Of  fishes,  166. 

Of  oysters,  123. 

Of  protozoans,  300. 
Diving  birds,  224. 
Division  of  amoeba,  289. 

Of  labor,  302,  303. 
Dogday  harvest  fly,  22. 
Dogfish,  168,  169,  178. 
Dogs,  279. 
Doves,  233. 
Down,  209. 
Dragon  fly,  13,  15. 
Drones,  46. 
Duckbill,  256. 
Ducks,  228. 
Dugong,  266. 
Dung  beetles,  40. 
Duodenum  of  man,  283. 

Of  pigeon,  215. 

Eagles,  233. 
Ears  of  owls,  234. 
Ear-shell,  136. 
Earthworms,  87. 


Earthworms,  distribution  of,  97. 

Muscles  of,  89. 
Eating  in  amoeba,  290. 

In  crayfish,  64. 

In  paramecium,  293. 

In  ruminants,  269. 

In  starfish,  335. 
Echinodermata,  331,  346. 
Echinoidea,  338,  347. 
Ectoderm  of  hydra,  313. 

Of  sponge,  308. 

Of  vorticella,  295. 
Ectoplasm,  286. 
Edentates,  259. 
Eels,  176. 

Lamprey,  153. 

Round-mouthed,  153. 
Efts,  192. 
Eggs  of  birds,  218. 

Of  crayfish,  73. 

Of  earthworm,  97. 

Of  fishes,  164. 

Of  hydra,  317. 

Of  jellyfish,  323. 

Of  medusa,  321. 

Of  snail,  134. 

Of  snake,  202. 

Of  sponges,  311. 

Shell,  219. 
Egret,  229. 

Elasmobranchii,  168,  180. 
Electric  fishes,  164. 

Light  bugs,  18. 

Ray,  170. 
Elephant,  277. 

Elk,  273,  275  (Frontispiece). 
Embryo  of  sponge,  311. 

Of  tapeworm,  349. 
Emu,  222. 

Enamel  of  rabbit's  teeth,  248. 
Encysted  amoeba,  289. 
Endoderm  of  hydra,  313. 

Of  sponge,  308. 

Of  vorticella,  295. 
Endoplasm,  286. 
Entomostraca,  83. 
Epicranium  of  grasshopper,  4. 
Epidermal  plates  of  turtle,  205. 
Epidermis  of  clam,  109. 
Epiglottis  of  rabbit,  250. 


364 


Index. 


Equilibrium  sense  of  crayfish,  72. 

Of  perch,  161. 
Ermine,  282. 
Esophageal  collar,  70. 

Of  grasshopper,  8, 9. 

Ring,  70. 
Ewes,  271. 
Excretion  in  amoeba,  291. 

In  crayfish,  69. 

In  earthworm,  95. 

In  frog,  185. 

In  grasshopper,  8. 

In  paramecium,  293. 

In  perch,  161. 

In  pigeon,  216. 

In  rabbit,  252. 

In  snail,  130. 

In  snake,  202. 
Exumbrella,  321. 
Eyed  elater,  41. 
Eyes  of  grasshopper,  8,  9. 

Of  snail,  133. 

Of  snake,  199. 

Of  squid,  139. 

Facial  angle,  282. 
Falconidae,  233. 
Fangs  of  snakes,  203,  204. 
Feathers,  development  of,  208. 

Distribution  of,  209. 

Kinds  of,  209. 

Structure  of,  208. 
Feather  stars,  331,  345,  347. 
Feet  of  pigeon,  212. 
Femur  of  grasshopper,  4. 
Ferret,  282. 

Fertilization  of  sea  urchin's  egg,  342. 
Filament,  gastric,  of  jellyfish,  323. 

Mesenterial,  326. 
Finches,  239. 
Fins  of  fishes,  163. 

Of  perch,  154. 
Firefly,  42. 
Fish,  154, 170. 

Brain,  285. 

Hatcheries,  166. 

Laws,  166. 
Fish  ways,  166. 
Flagella,  297. 

Of  hydroid,  320. 


Flagella  of  sponges,  307. 
Flatfishes,  163,  175. 
Flatworms,  348. 
Flesh  eaters,  278. 
Flight  of  pigeon,  208. 
Flippers  of  seals,  282. 
Floating  of  fish,  155. 
Flounder,  166,  175,  176. 
Flukes  of  whale's  tail,  265. 
Flycatchers,  239. 
Flying  fish,  176. 

Foxes,  265. 

Muscles  of  pigeon,  211. 
Food  of  clam,  113. 

Of  crayfish,  64. 

Of  earthworm,  92. 

Of  frog,  1 8 1. 

Of  perch,  156. 

Of  pigeon,  214. 

Of  rabbit,  247. 

Of  sea  urchin,  341. 

Of  snake,  200. 

Of  squid,  142. 

Of  starfish,  335. 

Food  balls  of  paramecium,  292,  293. 
Food  fishes,  165. 
Food  vacuole,  286,  287. 
Foot  of  clam,  105, 106,  108. 

Of  snail,  129. 
"  Form  "  of  rabbit,  246. 
Fossils,  285. 

Birds,  242. 

Bird  tracks,  207. 

Brachiopods,  354. 

Crinoids,  345. 

Reptiles,  207. 
Fox,  279. 
Fresh-water  clam,  102. 

Sponges,  310. 
Frogs,  181,  192. 
Function,  305. 
Functions  of  animals,  304. 
Fur  of  rabbit,  246. 

Gall,  51. 

Flies,  51. 

Gnat,  35. 

Gallinaceous  birds,  230. 
Gallinae,  230. 
Game  birds,  244. 


Index. 


365 


Game  fishes,  172. 
Ganglions  of  clam,  117. 

Of  crayfish,  70,71. 

Of  frog,  188. 

Of  grasshopper,  8. 
Ganoids,  177. 
Gar  pike,  177. 
Garter  snake,  200. 
Gastric  filaments  of  jellyfish,  323. 

Pouches  of  jellyfish,  323. 
Gastropods,  127. 
Geese,  228. 
Gemmule,  311. 

Genital  plates  of  sea  urchin,  341. 
Gephyrea,  101. 
Giant  water  bug,  18. 
Gila  monster,  198. 
Gill  chamber  of  crayfish,  68. 

Paddle  of  crayfish,  68. 

Rakers  of  perch,  160. 

Scoop  of  crayfish,  68. 
Gills  of  clam,  HI,  113. 

Of  crayfish,  66,  67. 

Of  dragon-fly  larva,  13. 

Of  mud  puppy,  191. 

Of  perch,  158. 

Of  sea  slug,  135. 

Of  siren,  190. 

Of  snail,  134. 

Of  tadpole,  189. 
Giraffe,  277. 
Gizzard  of  earthworm,  89,93. 

Of  pigeon,  215. 

Gland  cells  of  sea  anemone,  326. 
Glands,  digestive,  of  crayfish,  65,  66. 

Digestive,  of  starfish,  334. 

Green,  of  crayfish,  69. 

Salivary,  of  rabbit,  250. 

Scent,  282. 

Setigerous,  90. 
Glass-snake,  199,  205. 
Globigerina,  298,  299. 
Glochidia,  118. 
Glowworm,  42. 
Gnathostomata,  148. 
Gnawers,  260. 
Goats,  272. 
Gonads  of  jellyfish,  323. 

Of  medusa,  321.    ' 
Gopher,  pouched,  263. 


Gopher  turtle,  206. 
Gorilla,  282,  283. 
Gossamer,  58. 
Grasshopper,  i,  12,  15. 
Grebes,  224. 
Grizzly  bear,  281. 
Grosbeak,  cardinal,  239. 

Rose-breasted,  239. 
Ground  beetle,  39. 
Grouse,  231. 
Growth  of  amoeba,  290. 

Lines  of  clam,  103. 

Of  clam  shell,  no. 

Of  crayfishes,  74. 
Grubs,  38. 
Guinea  fowl,  232. 

Worm,  352. 
Gullet  of  cow,  270. 

Of  earthworm,  89,  93. 

Of  man,  283. 

Of  paramecium,  292. 

Of  perch,  157. 

Of  rabbit,  250. 

Of  sea  anemone,  325. 

Of  snake,  201. 
Gulls,  225. 
Gymnophiona,  195. 

Haddock,  165. 
Hagfishes,  153. 
Hair  worms,  351. 
Hake,  165. 
Halibut,  166,  176. 
Halteres,  36. 
Hand,  282. 
Hare  lip,  255. 
Hares,  260. 
Harvestmen,  60. 
Hawk,  cooper's,  233. 

Fish,  233. 

Sharp-shinned,  233. 
Hawkbill  turtle,  205. 
Hawk  moth,  28,  29. 
Head  of  pigeon,  214. 

Of  squid,  139. 

Of  tapeworm,  349. 
Heart  of  crayfish,  68,  69. 

Of  grasshopper,  6. 

Of  rabbit,  249,  250,  251. 
Heat-production  in  amoeba,  291. 


366 


Index. 


Hedgehog,  264. 

Heel  of  pigeon,  212. 

Hell-diver,  224. 

Hemiptera,  18. 

Hermit  crab,  81,  82. 

Herons,  229. 

Herring,  166. 

Hessian  fly,  35. 

Heterocercal  tail,  162. 

Hexacoralla,  328. 

Hibernation  of  frog,  186. 

Hind  wing  of  grasshopper,  4. 

Hinge  ligament  of  clam,  103,  106,  107. 

Teeth  of  clam,  cardinal,  104. 
Lateral,  104. 
Hippopotamus,  269. 
Hive  of  honey  bees,  46. 
Hog,  269. 

Hollow-horned  ruminants,  270. 
Holothuroidea,  343,  347. 
Homocercal  tail,  162. 
Honey,  47. 

Bee,  44,  45. 

Comb,  47,  48. 

Comb  of  cow,  270. 

Dew,  50. 
Hoofs,  266. 

Hooks  of  tapeworm,  349. 
Horned  toad,  198. 
Hornets,  49. 

Horns  of  ungulates,  270,  273. 
Horny  sponges,  309. 
Horse,  267. 

Fly,  33,  34- 
House  fly,  32. 
Humming  bird,  238. 

Moth,  28. 

Humming  miller,  28. 
Hydra,  313. 

Hydroids,  317,  318,  319. 
Hydrotheca,  320. 
Hydrozoa,  317. 
Hyena,  280. 
Hymenoptera,  44. 
Hypostome  of  hydra,  313. 

Of  hydroid,  319. 

Ichneumon  flies,  51. 

Iguana,  198. 

Incisors  of  rabbit,  248. 


Incubation,  219. 

Indigo  bird,  239. 

Individual,  306. 

Ink  bag  of  squid,  140. 

Ink  galls,  52. 

Insecta,  I. 

Insect  eaters,  263. 

Interambulacral    plates  of   sea  urchin, 

339- 

Intestinal  worms,  351. 
Intestine  of  clam,  115. 

Of  crayfish,  64,  66. 

Of  frog,  182,  183. 

Of  man,  283. 

Of  perch,  157. 

Of  pigeon,  215. 

Of  rabbit,  249,  250. 

Of  snake,  201. 

Of  starfish,  335. 
Irritability,  289. 
Isqpoda,  84. 
Itch  mite,  60. 

Jackal,  279. 
Jack  rabbit,  260. 
Jacksnipe,  230. 
Jaguar,  279. 
Jay,  239. 

Jellyfishes,  323,  324. 
Joint-snake,  199. 
June  bug,  36,  37. 

Kangaroo,  259. 
Katydid,  12. 
Keel  of  pigeon,  211. 
Keyhole  urchin,  343. 
Kidneys  of  clam,  115,  116. 

Of  crayfish,  69. 

Of  earthworm,  96. 

Of  frog,  182,  185. 

Of  perch,  157,  161. 

Of  pigeon,  215,  217. 

Of  rabbit,  249,  252. 

Of  snail,  130. 

Of  snake,  201,  202. 
Killdeer,  230. 
Kingbird,  239. 
King  crab,  85. 
Kingfisher,  237. 
Kiwi.  222. 


Index. 


367 


Labrum  of  grasshopper,  4. 
Lac  insect,  24. 
Ladybug,  41,  44. 
Lake  trout,  165. 
Lamb,  271. 
Lamp  shells,  354. 
Lamprey  eels,  153. 
Lancelet,  151. 
Language,  283. 
Larva  of  dragonfly,  13. 
Lateral  line  of  perch,  154. 
Leaf  rollers,  31. 
Leech,  100. 
Left-hand  shells,  128. 
Lemur,  282. 
Leopard,  279. 
Lepidoptera,  25. 
Lice,  24. 
Limestone,  299. 
Limnea,  134. 
Limpet,  136. 
Lingual  ribbon,  129. 
Lion,  279. 

Mountain,  279. 

Sea,  282. 

Lip  of  snail  shell,  127. 
Liver  of  frog,  182. 

Of  pigeon,  215. 

Of  rabbit,  249,  250. 

Of  snake,  201. 
Liverfluke,  350. 
Lizard,  196,  197. 
Lobster,  63,  77. 

Pot,  77. 
Locomotion  of  amoeba,  287,  290. 

Of  clam,  108. 

Of  crayfish,  62. 

Of  earthworm,  91. 

Offish,  155. 

Of  frog,  181. 

Of  grasshopper,  3. 

Of  hydra,  316. 

Of  rabbit,  247. 

Of  sea  urchin,  340. 

Of  snake,  200. 

Of  starfish,  332,  334. 
Locust,  it,  12. 

Long-winged  swimmers,  225. 
Loon,  224,  225. 
Lung-book  of  spider,  56. 


Lung-fish,  179. 

Lungs  of  frog,  182,  183. 

Of  pigeon,  215,  216. 

Ol  rabbit,  249,  251. 

Of  snake,  201. 

Of  spider,  56. 

Lymphatic  system  of  frog,  185. 
Lynx,  279. 

Macaws,  237. 
Mackerel,  165,  171. 
Macronucleus  of  paramecium,  292. 

Of  vorticella,  295. 
Macrura,  84. 
Madreporic  body,  332. 

Canal,  334. 

Plate,  333. 
Maggot,  34. 
Malacostraca,  83. 
Mallard,  228. 
Mammalia,  246,  256. 
Mammoth,  278. 
Man,  282. 
Manatee,  266. 

Mandible  of  grasshopper,  2, 4. 
Mantid,  13. 
Mantle  of  clam,  104. 

Lines,  109. 

Of  squid,  139. 
Manubrium,  321. 
Manyplies,  270. 
Maple  scale  insect,  23. 
Marmoset,  282. 
Marsipobranchii,  153. 
Marsupial,  257. 

Bone,  257. 
Marten,  282. 
Martin,  240. 
Mascalonge,  167. 
Mastodon,  278. 
Maxilla  of  grasshopper,  4. 
May  fly,  14. 
May  beetle,  36. 
Meadow  lark,  239,  242. 
Measuring  worm,  31. 
Medusa  bud,  320. 
Medusae,  321. 
Megatherium,  260. 
Menhaden,  165. 
Mesenterial  filaments,  326. 


368 


Index. 


Mesenteries  of  sea  anemone,  326. 

Of  starfish,  335. 
Mesentery  of  rabbit,  251. 
Mesoderm  of  sponge,  308. 
Mesogloea  of  Hydra,  313. 
Mesothoiax  of  grasshopper,  2. 
Metamorphosis,  30. 
Metathorax  of  grasshopper,  2. 
Metazoa,  300. 
Mice,  262. 
Micronucleus  of  paramecium,  292. 

Of  vorticella,  295. 
Mid  brain,  285. 
Midges,  34. 
Migration  of  birds,  220. 

Of  fishes,  165. 
Milkweed  butterfly,  25. 
Milliped,  54. 
Mimicry,  31. 
Mink,  282. 
Mite,  9,  60. 

Mocking  bird,  240,  241. 
Molars  of  rabbit,  248. 
Mole,  263. 
Mollusca,  102. 
Molluscoida,  353. 
Monarch  butterfly,  25,  26,  31. 
Monitor,  198. 
Monotremata,  256. 
Moose,  273,  276,  277. 
Mosquito,  35. 

Hawk,  14. 
Moss  animals,  354. 
Mother  Carey's  chickens,  226. 
Mother-of-pearl,  136. 
Moths  and  butterflies,  28. 
Motion  of  amoeba,  287,  290. 
Molting  of  birds,  219. 

Of  crayfishes,  74. 

Of  king  crab,  85. 

Of  snakes,  204. 

Of  spiders,  56. 
Mountain  lion,  279. 

Sheep,  271. 
Mourning  doves,  233. 
Mouse  brain,  285. 

Hawk,  240. 
Mouth  of  earthworm,  92. 

Of  hydra,  313,  314. 
Mud  eel,  190. 


Mud  fish,  178. 

Nest,  180. 

Puppy,  191. 
Mule  deer,  275. 
Mullet,  165. 
Multiplication  of  amoeba,  289. 

Of  hydra,  317. 

Of  hydroids,  321. 

Of  paramecium,  294. 

Of  protozoa,  296. 
Muscle  pectoral  of  pigeon,  211. 

Scars  of  clarn  shell,  103,  104. 

Subclavian  of  pigeon,  212. 
Muscles  of  clam,  106,  109. 

Of  crayfish,  62. 

Of  earthworm,  89,  92. 

Of  grasshopper,  3. 

Of  sea  anemone,  327. 

Of  starfish,  331. 
Mussel,  salt-water,  124. 
Myriapoda,  54. 

Natica,  134,  135. 
Nautilus,  144. 
Neck  of  pigeon,  214. 
Necturus,  191. 
Nemathelminthes,  351. 
Nematocysts  of  hydra,  315. 
Nereis,  99. 

Nerve  collar  of  earthworm,  89. 
Nerve  ring  of  crayfish,  71. 

Of  earthworm,  96. 
Nervous  system  of  clam,  117. 

Of  crayfish,  70,  71. 

Of  earthworm,  96. 

Of  frog,  187,  188. 

Of  grasshopper,  8. 

Of  pigeon,  217. 

Of  rabbit,  249,  254. 

Of  sea  urchin,  341. 

Of  snail,  130. 

Of  squid,  142. 

Of  starfish,  336. 

Nettle  cells  of  sea  anemone,  326. 
Neuroptera,  24. 
Newts,  192. 
Nighthawk,  238. 
Noctiluca,  298. 
No-see-ems,  34. 
Notochord,  148. 


Index 


369 


Nucleus,  286,  287,  301. 

Of  paramecium,  294. 
Numbfish,  170. 
Nuthatch,  241. 
Nymph,  13. 

Octocoralla,  329. 

Octopus,  143. 

Odonata,  13,  15. 

Odor  of  snakes,  204. 

Oil  gland  of  pigeon,  215,  217. 

Olfactory  lobe,  285. 

One-celled  animals,  286. 

Opercle  of  perch,  154,  160. 

Operculum  of  snail,  128,  129. 

Ophiuroidea,  337,  347. 

Opossum,  257,  258. 

Oral  arms  of  jellyfish,  323. 

Surface  of  starfish,  331. 
Orang-utan,  283. 
Organism,  305. 
Organs,  304. 
Orioles,  239,  243. 
Orthoceras,  144. 
Orthoptera,  12. 
Osculum  of  sponge,  307. 
Osphradia  of  snails,  130. 
Osprey,  233. 
Ossicles  of  sea  urchin,  338. 

Of  starfish,  331. 
Ostracoda,  83. 
Ostriches,  222,  223. 
Otter,  282. 
Ovary  of  bird,  218. 

Of  crayfish,  65. 

Of  earthworm,  89,  91. 

Of  frog,  182,  183. 

Of  grasshopper,  10. 

Of  hydra,  313,  317. 

Of  perch,  157. 

Of  sea  urchin,  341. 

Of  snake,  201. 
Oviduct  of  crayfish,  65. 

Of  earthworm,  97. 

Of  frog,  182,  183,  189. 

Of  grasshopper,  10. 

Of  perch,  157,  162.     • 

Of  pigeon,  215,  219. 

Of  snake,  201. 
Ovipositor  of  grasshopper,  10. 


Ovum,  302. 
Owls,  234,  235. 
Oyster,  122. 

Crab,  79,  80. 

Distribution  of,  123. 

Season,  123. 

And  starfish,  335. 

Palp  of  clam,  in,  114. 
Palpus  of  grasshopper,  4. 
Pancreas  of  pigeon,  215. 

Of  rabbit,  249,  250. 

Of  snake,  201. 
Panther,  American,  279. 
Paramecium,  291,  292. 
Parasites  of  grasshopper,  9. 

Of  rabbit,  252. 
Parasitic  arachnids,  60. 

Birds,  220. 

Crustacea,  83. 

Hymenoptera,  52. 

Protozoa,  297. 

Worms,  349,  351,  352. 
Parrakeet,  236,  237, 
Parrots,  236. 
Partridge,  231. 
Paunch  of  cow,  270. 
Peafowl,  232. 
Pear-tree  slug,  51. 
Pearls,  126. 
Peccary,  269. 
Pectinatella,  354. 
Pedicellariae  of  sea  urchin,  340. 

Of  starfish,  332. 
Pelecypoda,  102. 
Pelican,  228. 
Pen  of  squid,  139. 
Penguins  225. 
Perch, 154. 

Development  of,  162. 

Fins  of,  154. 

Opercle  of,  154,  160. 

Ringed,  154. 

Sea,  171. 
Perching,  213. 

Birds,  239. 

Pericardium  of  clam,  115. 
Periodical  cicada,  22. 
Perisarc  of  hydroid,  320. 
Perissodactyls,  267. 


Index. 


Peristaltic  action,  94. 

Peritoneum  of  rabbit,  251. 

Petrels,  226. 

Pewee,  239,  240. 

Pharynx  of  earthworm,  89,  92. 

Pheasants,  232. 

Phyllopoda,  83. 

Phylloxera,  24. 

Physa,  134. 

Pickerel,  166,  167. 

Pigeon,  208. 

Origin  of,  218. 
Pigment  in  fishes,  164. 
Pike,  166, 167. 

Perch, 171. 
Pinchers  of  crayfish,  73. 

Of  sea  urchin,  340. 

Of  starfish,  332. 
Pin  feathers,  209. 
Pinnigrade  animals,  282. 
Pinworm,  351. 
Pisces,  168. 

Placental  mammals,  259. 
Plaice,  176. 
Planorbis,  127,  134. 
Plant  lice,  23. 
Plantigrade  animals,  280. 
Plastron,  205. 
Plates,  epidermal,  of  turtle,  205. 

Genital,  of  sea  urchin,  341. 
Platyhelminthes,  348. 
Plovers,  230. 
Plumes  of  egret,  229. 

Of  ostrich,  222. 

Poison  gland  of  honey  bee,  46. 
Poisonous  snakes,  203. 
Polishing  powders,  299. 
Pollen  baskets,  46. 
Polyp,  coral,  325,  328. 

Fresh-water,  313. 
Polyphemus,  30. 
Polyzoa,  354. 
Pond  snails,  129, 133. 
Porcupine,  261. 
Porifera,  307. 
Pork  worm,  352. 
Porpoise,  266. 
Portal  vein  of  perch,  159. 
Portuguese  man-of-war,  322,  323. 
Potato  beetle,  39. 


Prairie  dog,  263. 

Hen,  231. 

Wolf,  279. 
Prawns,  77. 
Prey,  birds  of,  233. 
Primaries,  210,  211. 
Primates,  282. 
Proboscis  of  elephant,  277 

Of  snail,  133. 
Proglottids,  349. 
Pronghorn,  273. 
Propagation  of  fishes,  166. 
Propolis,  47. 
Proteid,  301. 

Prothorax  of  grasshopper,  2. 
Protoplasm,  286,  300,  301. 
Prototheria,  256. 
Protozoa,  286,  296,  300. 

Colonial,  305. 

Distribution  of,  300. 

Shell-bearing,  298. 
Proventriculus  of  pigeon,  215, 
Psalterium  of  cow,  270. 
Pseudopod,  286,  287. 
Ptarmigan,  231. 
Puffins,  225. 
Puma,  279. 
Puparium,  33,  34. 
Purple  finch,  239. 

Quahog,  121. 

Quail,  231. 

Queen,  honey  bee,  46. 

Cells,  48. 
Quills,  209. 

Of  porcupine,  261. 

Rabbit,  246. 

In  Australia,  253. 

Development  of,  254. 

Nervous  system  of,  254. 

Structure  of,  249. 
Raccoon,  281. 
Rails,  230. 
Raptores,  233,  235. 
Ratitae,  222. 
Rats,  262. 

Rattlesnake,  203,  204. 
Rays,  168,  169. 

Of  starfish,  331, 


Index. 


Recovery  of  earthworms,  98. 

Of  hydra  from  mutilation,  317. 

Of  starfish  from  mutilation,  335. 
Rectum,  283. 
Red  coral,  329. 

Deer,  274. 
Rennet,  270. 

Reproduction  of  amoeba,  289,  291. 
Reptiles,  196. 

Age  of,  207. 

Extinct,  207. 
Respiration  in  amoeba,  290. 

In  clam,  no. 

In  crayfish,  66. 

In  earthworm,  95. 

In  frog,  183. 

In  gastropods,  130. 

In  grasshopper,  5. 

In  perch,  158.  - 

In  pigeon,  216.  * 

In  rabbit,  251. . 

In  sea  urchin,  341. 

In  snail,  133. 

In  snake,  201.   - 

In  squid,  142. 

In  starfish,  336. 

Restoration  of  limbs  in  crayfish,  75. 
Reticulum  of  cow,  270. 
Rhinoceros,  268. 
Ribs  of  snake,  199,  200. 
Right-hand  shell,  128. 
Ringed  perch,  154, 171. 
Robin,  241. 
Rodents,  260. 
Rose  slug,  51. 
Rotifers,  352,  353. 
Roundworms,  351. 
Rove  beetles,  41. 
Ruffed  grouse,  232. 
Ruminants,  269. 

Solid-horned,  273. 

Sage  hen,  231. 
Salamanders,  191. 
Salmon,  165,  174. 
Sand  cake,  343. 

Dollar,  343. 

Hoppers,  84. 

Star,  337,  338. 

Worm,  99. 


Sapsucker,  238. 
Sardine,  165. 
Sawflies,  51. 
Scale  bugs,  24. 
Scales  of  butterfly,  25. 

Of  fishes,  162. 

Of  lizard,  196. 
Scallop,  125. 
Scent  gland,  282. 
Scorpion,  60. 

Scutellum  of  grasshopper,  4. 
Scutes  of  snake,  200. 
Scutum  of  grasshopper,  4. 
Scyphozoa,  323. 
Sea  anemone,  325,  326. 

Cucumber,  331,  343,  344. 

Eggs,  339. 
.     Fans,  329. 

Lilies,  331,  345. 

Lion,  282. 

Mats,  354. 

P.ear,  149. 

Pen,  329. 

Perch,  171. 

Squirt,  149. 

Turtle,  205. 

Urchin,  331,  338,  339. 

Whip,  329. 
Seals,  282. 

Secondaries,  210,  211. 
Segmentation  of  egg,  342. 
Senses  of  clam,  118. 

Of  crayfish,  72. 

Of  earthworm,  97. 

Of  frog,  187. 

Of  gastropod,  130. 

Of  grasshopper,  8. 

Of  jellyfish,  323. 

Of  perch,  160,  161. 

Of  pigeon,  217. 

Of  rabbit,  255. 

Of  snake,  202. 

Of  squid,  142. 

Of  starfish,  336. 
Sepia  of  squid,  141. 
Serpent  stars,  338. 
Setae  of  earthworm,  90. 
Seventeen-year  locust,  22. 
Sexton  beetles,  41. 
Shad,  165. 


372 


Index. 


Sharks,  168, 169. 
Shedding  of  horns,  273. 
Sheep,  270. 

Shell  of  sea  urchin,  339. 
Shipvvorm,  123. 
Shore  birds,  230. 
Shrews,  264. 
Shrike,  240. 
Shrimp,  77. 
Silica,  299. 
Siliceous  earth,  299. 

Sponges,  309. 
Silkworm,  30. 
Silvertip  bear,  281. 
Sinus,  blood,  of  crayfish,  69. 
Siphon  of  squid,  140. 

Of  clam,  105,  108. 
Siren,  190. 
Skate,  169, 170. 
Skeleton  of  arthropods,  86. 

Of  birds,  245. 

Of  bony  fishes,  170. 

Of  insects,  52. 

Of  pigeon,  208,  213. 

Of  sea  urchin,  338. 

Of  shark,  168. 

Of  sponge,  308. 

Of  starfish,  331. 
Skin  of  earthworm,  90. 
Skipjacks,  41. 
Skippers,  35. 
Skunk,  282. 
Slaves  of  ants,  51. 
Slipper  animalcule,  291. 
Sloths,  259. 
Slugs,  132. 

Sea,  135. 
Smell  in  birds,  217. 

In  crayfish,  72. 

In  deer,  277. 

In  rabbit,  255. 

In  snails,  130. 
Smelling  patches,  130. 
Smelt,  165. 
Snails,  land,  131. 

Pond,  133. 

River,  134. 

Sea,  135. 

Shell,  127. 
Snake  doctors,  14. 


Snake  feeders,  14. 
Snakes,  199,  205. 

Brain,  285. 

Poisonous,  203,  204. 
Snipe,  230. 
Snout  beetles,  41. 
Social  bees,  49. 
Sole,  176. 

Solid-horned  ruminants,  273, 
Solitary  bees,  49. 
Sowbug,  84. 
Spanish  fly,  41. 
Sparrows,  239. 

Brain,  285. 

English,  239. 
Specialization,  304. 
Speech,  282. 
Sperm  cells  of  hydra,  317. 

Of  sponge,  311. 
Spermary  of  fish,  162. 

Of  hydra,  314,  317. 

Sea  urchin,  341. 
Sperms  of  hydra,  317. 

Of  jellyfish,  323. 

Of  medusa,  322. 

Of  sponges,  311. 
Sphinx  moth,  28. 
Spicules  of  sponge,  307,  308,  309. 
Spiders,  55. 

Jumping,  56. 

Trapdoor,  59. 

Web,  57. 
Spinal  bulb,  285. 

Cord,  285. 
Spindles,  14. 
Spines  of  sea  urchin,  338,  339. 

Of  starfish,  331. 

Of  sting  cells,  315. 
Spinnerets  of  spider,  57. 
Spinning  of  spiders,  56. 
Spiny-rayed  fish,  171. 
Spiracles,  5. 
Spleen  of  snake,  201. 
Sponges,  307. 

Calcareous,  308. 

Commercial,  309,310. 

Development  of,  311. 

Flagella,  307,  308. 

Fresh-water,  310. 

Horny,  309. 


Index. 


373 


Sponges,  in  reservoirs,  311. 

Siliceous,  309. 
Spongin,  309. 
Spoonbill  catfish,  178. 
Spouting  of  whales,  266. 
Spring  beetles,  41. 
Squash  bug,  20,  21. 
Squid,  138. 

Giant,  143. 
Squirrels,  263. 

Flying,  263. 

Fox,  263. 

Gray,  263. 

Red,  263. 
Stable  flies,  34. 
Stag-beetles,  40. 
Stake  driver,  229. 
Starfish,  331,  332. 

Development  of,  337. 
Sting  of  honey  bee,  46. 

Cells  of  hydra,  314. 

Cells  of  jellyfish,  323. 

Rays,  169. 
Stomach  of  crayfish,  65,  66. 

Of  frog,  182,  183. 

Of  jellyfish,  323. 

Of  man,  283. 

Of  perch,  157. 

Of  pigeon,  glandular,  215. 

Of  rabbit,  249,  250. 

Of  ruminant,  270. 

Of  sea  anemone,  326. 

Of  snake,  201. 

Of  starfish,  334. 

Stone  canal  of  starfish,  333,  334. 
Stork,  229. 
Striped  bass,  171. 
Sturgeon,  165,  177. 
'Subumbrella,  321. 
Suckers,  166,  173. 

Squid,  139. 

Sulphur-bottom  whale,  266. 
Sunfish,  171. 

Sutures  of  snail  shell,  127. 
Swallows,  240. 

Bank,  240. 

Barn,  240. 

Chimney,  238. 

Eave,  240. 

Fork-tail,  240. 


Swallowing  in  snakes,  199,  200. 

Swallow-tail  butterflies,  30. 

Swarming,  48. 

Swifts,  197,  238. 

Swim  bladder  of  perch,  155. 

Swimming  of  crayfish,  62. 

Of  frog,  1 8 1. 

Of  jellyfish,  321,  325. 

Of  perch,  155. 

Of  squid,  140. 
Syrinx  of  pigeon,  218. 

Tadpole,  189. 

Tail  fin  of  crayfish,  62. 

Of  squid,  140. 
Tails  of  fishes,  162. 
Tapeworm,  349. 
Tapir,  267,  268. 
Tarantula,  59. 
Tarsus  of  grasshopper,  4. 

Of  pigeon,  212. 
Taste  in  crayfish,  72. 
Teeth  of  rabbit,  248. 

Of  sea  urchin,  340. 

Of  snake,  199. 
Teleostei,  180. 
Teleostomi,  180. 
Temperature  of  amceba,  291, 

Oi  frog,  1 86,  187. 

Of  insects,  7. 

Of  mammals,  251,  283. 

Of  pigeon,  216. 

Of  rabbit,  251. 
Tentacles  of  hydra,  313. 

Of  jellyfish,  323. 

Of  sea  anemone,  325. 

Of  sea  slug,  135. 

Of  snail,  130,  131. 
Terns,  225. 
Tertiaries,  210,  211. 
Theria,  256,  257. 
Thistle  bird,  239. 
Thornbacks,  170. 
Thousand  legs,  54. 
Thread  capsules  of  hydra,  315. 
Thrush,  brown,  240. 

Wood,  240. 
Thumb  of  bird,  211. 
Tibia  of  grasshopper,  4. 
Ticks,  60. 


374 


Index. 


Tiger,  279. 

Beetle,  40. 
Timber  wolf,  279. 
Tissues,  304. 
Toads,  192. 

Brain,  285. 
Toes  of  pigeon,  212. 
Tomato  worm,  28. 
Tongue  of  snake,  199. 

Of  frog,  182. 

Of  woodpecker,  237. 
Torpedo,  170. 
Tortoise  shell,  205. 
Totipalmate  birds,  227. 
Touch  in  amoeba,  291. 

In  catfish,  173. 

In  clam,  118. 

In  crayfish,  72. 

In  earthworm,  97. 

In  frog,  187. 

In  grasshopper,  9. 

In  perch,  161. 

In  pigeon,  217. 

In  rabbit,  255. 

In  snail,  130. 

Tracheae  in  grasshopper,  5. 
Tracks  of  rabbit,  247. 
Tree  frog,  193. 

Toad,  193. 
Trematoda,  351. 
Trepang,  344. 
Trichina,  351,  352. 
Tridacna,  125. 
Trigger-hair  of  hydra,  315. 
Tripoli,  299. 

Trochanter  of  grasshopper,  2,  4. 
Trochantine  of  grasshopper,  2, 4. 
Trochelminthes,  352. 
Trout,  174. 

Tube  feet  of  starfish,  332. 
Tube-nosed  swimmers,  226. 
Tubularian  hydroid,  320. 
Tunicates,  148,  149. 
Turbellaria,  351. 
Turkey,  231,  232. 

Buzzard,  235,  236. 
Turtle,  boxshell,  205. 

Gopher,  206. 

Green,  205. 

Hawkbill,  205. 


Turtle,  sea,  205. 

Snapping,  206. 
Turtledove,  233. 
Tusks  of  elephant,  278. 
Tympanum  of  frog,  187. 
Typhlosole,  92,  94. 

Umbo,  102,  103. 
Ungulates,  266. 
Ureter  of  rabbit,  249,  252. 

Of  snake,  201. 
Urochorda,  148. 
Urodela,  195. 

Vacuole,  286, 292. 

Contractile,  295. 
Vane  of  feather,  208. 
Veil  of  jellyfish,  321. 
Veins  of  insect  wing,  3. 
Velum  of  medusa,  321. 
Velvet  of  antlers,  274. 
Ventral  plates  of  snake,  200. 
Vermiform  appendix,  283. 
Vertebrata,  148,  284. 
Viceroy  butterfly,  31. 
Vinegar  eel,  351. 
Voice  of  frog,  193. 

Of  pigeon,  218. 
Vorticella,  294. 
Vulture,  235. 

Waders,  230. 
Walking  stick,  12,  13. 
Wall-eye,  171. 
Warblers,  240. 
Wasps,  49,  50. 
Water  beetles,  42. 

Bug,  18. 

Bulbs,  of  starfish,  334. 

Dog,  191. 

Flea,  83,  84. 

Moccasin,  203. 

Snakes,  200. 

Tubes  of  sea  urchin,  340. 

Tubes  of  starfish,  332,  333. 
Wax  of  bees,  47. 
Weasels,  282. 
Weevils,  40,  41. 
Whalebone,  265. 
Whales,  265. 


Index. 


375 


Wheat  midge,  35. 
Wheel  animalcule,  352,  353. 
Whip-poor-will,  238. 
Whiskers  of  rabbit,  255. 
White  bass,  172. 
Whitefish,  165,  174. 
White-tail  deer,  274. 
Whorl  of  snailshell,  127. 
Wild  canary,  239. 

Cat,  279. 

Windpipe  of  snake,  201. 
Wing  of  pigeon,  209. 
Wireworm,  41. 
Wishbone,  213. 
Wolf,  279. 
Wolverine,  282. 
Woodchuck,  263. 


Woodcock,  230. 
Wood  duck,  228,  229. 
Woodpecker,  237. 

Yellow-bellied,  238. 
Worker,  honey  bee,  46. 
Worms,  348. 

Intestinal,  351. 
Wren,  240. 

Yellow  bass,  172. 
Jacket,  49. 
Perch,  171. 

Zooid,  319. 

Action  of,  320. 
Zoophytes,  319. 
Zygodactyl  feet,  237. 


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